You don't think the introduction of Metal is helping to bring back game developers?
In short - no. If they wanted to bring back game developers and that was their goal, they would've improved OpenGL support or used Vulkan instead. In fact, Metal is doing quite the opposite, as it pushed Apple to abandon further OpenGL support.
Long answer: no, because Metal is a proprietary API meant to be used only on Apple devices, which is fine on iOS where there is a huge market, but it really doesn't make much sense on Macs. It requires a lot of work for a niche segment of the market. It would be a lot different if there were many more Macs out there, but for gaming and game developers, it's really about quantity. There are no Mac-only games, and the only reason why there are any Mac games at all is because the cost of porting is usually low, so - why not? Maybe some extra dollars on the side. It's different with apps for designers or modelers and such - they are much more expensive, used by a smaller group of people that pay much more (Zbrush doesn't need to sell hundreds of millions of copies to be profitable with it's $800 price tag). And some of these people traditionally prefer Macs (for example, designers, photographers, certain illustrators, etc.) so that's where the market is, even if there are far less Macs than PCs out there. But for games - the only way you can have them on the Mac is to make porting so easy (in other words: cheap) that it's not a problem for developers to do it, alongside their main target: the PC or consoles.
So, why doesn't Metal help? Well, because you need to code specifically for Metal. If you code for OpenGL (and you do, if you want your game to run on Playstation), you can use it on PS, Windows and Macs, so that's not a problem - huge market and Mac is riding along. But with Metal you can only use for Mac computers. And it's not like you can just say "hey programmer, change our game from DirectX to Metal!" - you have to write your engine from the scratch to support it. And even if you use Unreal, for example, that supports Metal, you have to plan your game to use it from the start. It's a bit complicated to explain, but lets just say that it takes a lot of work - which costs money. This wouldn't be a problem at all if the profits from Mac were big enough to cover the expenses - it just so happens they are usually not. Blizzard does it - World of Warcraft supports Metal, for example. But then again, their Overwatch is not coming to the Mac, because of Apple's lack of OpenGL and driver support and it was too complicated (in other words: costly) for Blizzard to change the game to support Metal instead. In fact, if Apple really wanted to have gaming on the Mac, they wouldn't use Metal, they would improve their OpenGL support. Then, for example, Blizzard would say - hey, we're already doing OpenGL development of Overwatch for the PS4, why not do a Mac port as well. However, Overwatch relies on some modern OpenGL stuff that Apple didn't implement in macOS -
because they are invested in Metal. Sure, a game does run better on Metal than on OpenGL, but only on Macs.
If Apple wanted to replace OpenGL with a more low-level API (which improves performance, sure), and they were serious about gaming, they should've implemented Vulkan which works on PCs as well. In other words, they would've made it easier for developers to port for Mac, since they are already doing it for the PC.
So why did Apple do it? Why Metal? Well, first of all - because of iOS. There, Metal makes perfect sense. The market is so large, it's even more profitable than PC or consoles, and developers are crazy not to make a game work for iOS, if they are making a mobile game. So - for games that can run on iOS, the tables are turned. We're making an iOS game, we're doing the Metal thing, so why not do a Mac version too? (this is the reason there are a lot of iOS games that come to the Mac as well). And Apple wants more iOS games. The problem here is obvious - if you want to play iOS games, then it's great, but you won't find Uncharted 4 or Gears of War 4 on iOS.
Second - Metal is not just for games, and it allows Mac developers to make better apps. For example, a photo-editing app called Affinity Photo uses Metal and it runs great and it's exactly what Apple wants - to give their traditional developers better tools to work with. Apple doesn't care much about games, because that's not where their market is - sure, they'll bring along a developer or two on the keynote, but in reality, their whole hardware is turned towards people who use professional or office apps. But even there, Metal is not faring really well - while Adobe initially promised Metal support, they abandoned the idea - probably because they think OpenGL is fine as it is. A shame, but it's Apple's fault as much as Adobe's.
So, how can Apple turn the tide? Well, that's assuming they want to. Maybe in the future they decide they want to bring gaming to the Mac. It works well on iOS, gaming is a huge win for them there. I'm sure Apple wouldn't mind to repeat that with the Mac, but it probably is too much of an effort for them to do so, at this point. Even if they change their mind, the process would be slow.
1.
Hardware: They would have to improve the GPUs on their computers. This is, actually, more a matter of perception than a real problem. Modern iMacs can game even now. And the next generation will only do better. But, as I said, it's all about
perception. They need to attract gamers, and gamers want power, even if they don't really need it For example, Overwatch runs better on my base model iMac 5K - in Bootcamp - than it does on my PS4, but judging from the YouTube videos, you'd think you need latest and greatest GPUs to run the game - it's just how PC gamers think. No wander they call them "PC Master Race"

So Apple needs a couple of really powerful Macs to attract game bloggers and then attract their audience, etc. If you want, say, Angry Joe to use a Mac, you need a Mac with a GTX 1080, even better - with two. Then he can play on a Mac, say "Hey, this Mac is really great for gaming", and then people would buy other Macs for gaming and find out that you can play a lot of games on Mac hardware, even if it's not maxed out.
2.
Software: Apple would have to implement better OpenGL or Vulkan support until they get popular enough to attract gamers and developers. At that point, they can switch to Metal or whatever they want.
3.
Business: Apple would have to start building business relationships with game publishers. Make a lot of deals - with EA, Activision on one side, and build relationships with indie developers on the other. Invest a lot of money to make it work, invest a lot of time. Work with Steam. Improve their App Store to gather more people (instead of the joke that the Mac App Store is today). Basically, do what they are doing for iOS. Get Nintendo on board - like they did with iOS. Now that was huge. In fact, imagine if they could somehow make Mass Effect: Andromeda a timed exclusive for the Mac. That's practically impossible at this point, but just hypothetically, it would be huge. Sometimes, one game is enough to sell a system. Funny story: in fact, Halo was coming to the Mac and was announced on an Apple Keynote. Steve Jobs introduced Halo to the world. Then they lost Bungie to Microsoft, who offered them a better deal, and sold a bunch of XBoxes as result.
4.
Marketing: They would have to advertise the **** out of it all.
Apple is so huge and powerful, I actually think they
could do it. It would take time and effort, but they actually could do it. Who knows, maybe one day they do. But, it would take a lot of push, and Apple built it's business around an entirely different market. I doubt they will ever make a gaming machine out of a Mac. There is some hope they at least make it easier for developers to port games to the Mac and we get an occasional game or two. I hope they do something like that at least. Ironically, Metal is doing the exact opposite (actually not Metal itself, but the fact that they are abandoning OpenGL
because of Metal).
Sorry for the long reply
