It always amazes me at how people are so willing to take the side of massive corporations over individual consumers.
I side with whoever I believe is right. It does not matter whether that party is corporation or consumer, friend or foe.
Many will see this mandatory slowing down of phones as a way to convince people that it's time to buy an entirely new phone, not a new battery. Whether Apple's motives were genuine or not, it comes off as grubby and money grabbing.
If Apple really wanted to force its users to upgrade, why would they introduce a throttling feature which was pegged to the quality of the battery in your phone? That's a dead giveaway, because just like you said, a fresh battery solves the problem altogether. Why not simply have the software patch slow down your phone regardless of the health of your battery, if Apple wanted everyone to keep upgrading to the newest and greatest?
As it stands, Apple essentially had 5 options.
1) Throttle older iPhone performance in order to prevent the devices from shutting down unexpectedly.
2) Avoid throttling and just let the iPhones unexpectedly turn off.
3) Offer a battery swap program for older iPhone batteries.
4) Improve the power delivery system in order to handle deteriorating batteries.
5) Include larger batteries that can supply the needed power requirement.
Option 2 is obviously unacceptable. Option 3 works only for countries with a strong apple store retail presence; users in other countries or who are not comfortable with letting a third party do this are essentially out of luck. Option 4 appears to be what Apple is trying to do, what with news of them looking to design their own power management chips, but it doesn't address the current, immediate issue. Option 5 is still doable with the larger iPhone models (and indeed, it seems the plus models have not been affected as much as the smaller iPhone models), but unless you are willing to make the iPhone 8 and SE much thicker and heavier or drop them altogether, I don't see how this is feasible.
What this means is that in the short term at least, throttling your iPhone is still the most reasonable option with the best risk/reward in terms of the user experience of the hundreds of millions of iPhone users around the world overall, which is incidentally the one Apple went with. Every other option results in a major user experience tradeoff in one way or another. Obviously, some tech-savvy user is going to claim that replacing the battery is no mean feat for him, but don't forget - Apple doesn't make this sort of decision based on what is most convenient for a few tech-savvy individuals lurking around in Macrumours, and they rightfully shouldn't.
In a nutshell, the more I analyse the situation, the more I believe Apple is simply trying to make older iPhones usable the best way they can. You can argue that maybe they went about it the wrong way, and in hindsight they probably did, but it doesn't make their motives any less pure. It's not planned obsolescence, it's not greed, it's just Apple doing that their customers pay them to do - make the tough calls for them so they don't have to. And the downside of having to constantly second-guess what your users want is that sometimes, you just guess wrong.