It won't be top of the line, but I don't really see why it wouldn't still be usable at least.
And even if the person buying the phone today won't consider it usable for their needs in eight years time, they can still sell it to someone who doesn't have a need for a high spec'ed phone.
I think you can look at it similarly to how one would look at an 8 year old laptop today.
A decently spec'ed laptop from 2015 is still very usable today, as long as you keep your expectations reasonable.
I have a Galaxy S4 and it's basically unusable at this point. I was able to install LineageOS and the home screen feels okay, but it stutters like hell when I do anything more demanding such as browsing YouTube.
Hmm, Newpipe works fine for me but really heavy websites definitrly are a pain, still clearly usable all in all tho and considering how much slower smartphone development is now I have no doubts a good device will be usable in eight years, you can look at the computer side to tell that hardware requirements for general use probably won't increase much for the forseeable future!
Idk why video calls and Whatsapp wouldn't work but I never used the normal Youtube app so all I can tell you is that Newpipe still works great, the official Youtube website is definitely a pain like any JS heavy piece of garbage. Not sure why you would have a bad experience with old Laptops unless they break or you try to run Windows on one, if you got at least 2GB of RAM in it you should be fine in my experience but 4GB is more ideal these days.
That's a valid concern, but it also assumes that the requirements for apps will go up in a similar trend as they did in the previous 8-10 years.
I'm not entirely convinced that they will. Smartphones 10 years ago were still very much a developing product category, whereas I think today they are generally matured.
Just look at laptops as a comparison. When they were still rapidly developing, an eight year old laptop would have pretty much been obsolete. But today an eight year old laptop will still serve most people perfectly fine.
That's rubbish, 2018 most laptops were using 8th gen Intel CPUs, and they still work fine today for web-browsing and doing word processing and not too heavy spreadsheet work. An i5 from that era is still perfectly usable.
Browsers will never have a higher requirement. It's the particular websites that will use newer technologies that older browsers may not support.
It may not be a mainline browser, but there's no reason you couldn't grab a new browser made to allow your currently out of date phone to use newer features, or at least the features your phone supported at launch. A cursory search on fdroid showed at least 1 browser with a requirement of android 4.4+.
The main thing to remember is that every website doesn't take more power or newer technologies than the last. It's only very specific situations where anything will need more power than something had 5 years ago. 99% of my apps could run on anything probably just fine. Email, Music, Audiobooks, VPN, 2FA etc. Most of those probably have security checks requiring a minimum OS version. Meaning they would actually work for longer on a phone with longterm OS updates than a phone that's much stronger.
With the obvious exception being games. But I would never recommend thinking long term about games in any circumstance.
My phone is 2 years old for me. I bought a oneplus 8 refurb in 2020 for Christmas. Unlocked and outright. I got it because my Galaxy S9 before that was Verizon locked, and I just got off my parent's phone plan. Verizon is very expensive.
I'll still use my old phone from time to time. Mainly for dual account Pokemon Go, or plug it up to a TV to watch something that doesn't support cast, like Newpipe.
I'll keep this phone as long as I can. It's on its last update, though. I'll use LineageOS when I can.
I don't really feel that my 4a slowed down, but the battery is degraded for sure. Battery life was never amazing, but now it's just bad. So this is why I am looking at the Fairphone: If I could just swap my battery easily, I would just continue using my 4a.