Security is mostly a psychological game, it's far easier to trick a person into doing something than by doing it through deep diabolical digital subterfuge. So, everyone is going down the route of app stores, signing, and clickable hurdles. They're securing their side and reminding you that you are installing something, it's not a passive 'OK.' It's another of those Modern Life is Rubbish things, but the fact is that people will install any old shit they find on the internet and then be surprised that someone wants umpteen bitcoins to unlock their computer.
I agree that Microsoft has a hard job with Windows, they have to support infinite hardware combinations, etc. That's fine, but I'm happy for that to be their problem and not mine. If you want hardware choice, to pick your favourite graphics card, etc. than Apple probably isn't for you. I'm not sure why people get so het up about that, it's not like they're keeping their business model a secret. I'm not sure that people buy Apple computers just to look cool, there's an off-chance they might actually like using them.
My 2009 Mac Mini doesn't run the latest MacOS (High Sierra, if I recall) but still gets security updates, so I think that's a reasonable lifespan.
Adobe and Affinity are much the same on either platform and file interchange isn't an issue, even fonts (mostly, if you don't use anything from Microsoft) play nice on both systems. But on the design side, most people will have been brought up with Macs, so that familiarity is there.
To be honest, all computers these days are generally overpowered for most users. When I need mothership-grade power, I offload the processing to Amazon because it's an order of magnitude more than could be managed on a laptop.
As to making money, I don't have a issue with App Stores taking a cut. I spend my business life with end-users telling me that the products we offer should be free, which is great, but we've never figured out how to the get the 65 developers involved (not to mention everyone else) to work for free. Trust me though, management are working on that.