That is the price to be paid for being on the "cutting edge". Personally, I think it is a losing battle (trying to constantly be on the cutting edge).
Now, I'm a software developer and until about 6 months ago, I was perfectly happy using OS X Snow Leopard on my (personal) mid-2009 MBP. 8 years on, I upgraded to Sierra, and finally decided to upgrade the hardware (SSD, more RAM). I'm certain that this will last me years without any problems, and will solve far more of my computing problems than I can ever conceive of.
My point being ... you can be perfectly happy with a slightly "older" OS on an older MBP. The insistence on having the latest and greatest OS/apps/gadgets is a pursuit of inevitable frustration ... just the kind of pursuit that Apple or any other computer manufacturer wants for you, so that you keep running to them, crying, begging for the latest and greatest that they have to offer, in exchange for $$$$.
In that sense, it is not all that dissimilar from the kind of dependency you develop on a drug dealer who keeps raising the price for a gram, because he knows that the amount that got you high a month ago is not going to be enough now, and you need more drugs and you're more desperate for them
This is not a judgment of you or anyone else ... just what I think the tech industry does to us consumers.