> someone decided to change something and deprecate the older stuff
I definitely understand the pain. In some cases, it's stupid moves. In other cases, it's about reclaiming the resources for something better. With wireless, should a small number of people who want to use old devices mean that we can't use those wireless frequencies for newer high-speed data? Maybe carriers should start pricing based no how much bandwidth you're using in terms of frequencies. Well, you're using a device that is 1/10th as efficient as a modern device so we're charging you many times more than what we charge customers with modern devices.
Sometimes there's inefficient stuff that impacts whether others can enjoy what they want.
> But what is the alternative?
The alternative is that we decide that new stuff (possibly progress) isn't something we want. I say possibly progress because some stuff is questionably progress. Do we need YouTube, TikTok, online games, etc? No, but they can surely be nice. We could certainly go back to the days of 2GB wireless plans and live like that. Heck, we lived without wireless data for a long time.
With some of the software churn, it just becomes hard to support so many different configurations and people concentrate on the ones that are commonly used.
> keep up with everything and partake in more consumerism than I should
Some of it is consumerism. Some of it is progress. I think you're slightly unfairly conflating it all as consumerism. The ability to offer unlimited data plans and faster data speeds is progress over slow, limited data plans. The problem you're facing is that everyone else changes and you don't see the point of it. Imagine everyone started speaking NewEnglish. You might see nothing wrong with English and it's not like English no longer works, but given that everyone else has changed, it no longer works for what you want - communicating with others around you.
Realistically, this is part of living in a civilization. You have to go along with what the civilization is doing and what will interface with them. This isn't even a modern phenomena in some ways. You talk about having an old computer that you want to be able to interface with others safely (view modern web pages, keep running software, etc). I'm now thinking of the Reformation where literally if you didn't adopt the new religion you might be killed. That's an extreme example, but there's a lot that people must do to be a part of our civilization.
Humans are social beings and our technology is no less social. It's why people have fights over things like programming languages. If PHP is a "dead language" it means that the next generation of engineers won't learn it and it will become less useful over time because fewer people will be improving it, writing libraries for it, and fewer systems will support it well. If a lot of people leave Android for iOS, there will be fewer apps for Android, fewer device options, etc. It's why people have fights over which next-gen console will win - because if they pick the losing device, they might not get a lot of games. I mean, if you bought a Dreamcast, you ended up buying something that never realized its potential because of the social context where game devs didn't make enough games for it.
Our technology is social. If you're not going along with that social context, you're going to miss out on things. In a certain way, you want everyone to support what you like even if it doesn't make sense for them (in terms of time and money).
Again, I understand the pain and there is a lot of consumerism. However, there's also progress in the mix as well. As the social context of the tech changes, you have to keep up with it to an extent. Companies don't want to keep supporting a 20-year-old OS because a few people don't see the need for the new features introduced in newer versions. Should you pay for a support contract for the old OS you want updates for? How expensive should that be given how few people will be paying for the engineering time to make that happen? Likewise, if 3G users want to keep their network around, how much should they pay for their plans to compensate for the fact that they're using a much greater share of a scarce resource (wireless spectrum)? $500/mo rather than $50/mo? It kinda gets to the point that it's realistically impossible since someone isn't going to pay $500/mo instead of upgrading their phone. Likewise, you aren't going to pay thousands per year for a support contract on an obsolete OS.