It is perfectly reasonable for hardware this old or older to still be in use. But by virtue of being standard in pretty much all new hardware for 6-7 years now, HEVC support is far more ubiquitous in 2022 than AV1.
More importantly, I cannot feasibly bring my RTX 3080 with me on a plane. When loading up movies before I travel, I need them in a codec supported by my phone or tablet. HEVC has fit that bill for years now, and will continue to do so until AV1 support has become ubiquitous in mobile hardware and my current devices have been retired.
Software decoding should also work on a $100 cpu.
You don't always get to decide. E.g. IP cameras will generally support both h.264 and h.265 these days, with HEVC doing vastly better than AVC, yet if that output has to go near a browser, instead of through dedicated software... SOL. Can't do anything with it. The hardware can, the software can't.
And AV1 is decode-only anyway, and only supported in the newest platforms. CPU decoding is just not a reasonable solution.
Going with AV1 is not an option for the vast majority of people as it requires hardware support. If you try using AV1 on a computer that didn't come with a hardware decoder for it, your machine will crawl.
I force h264 in YouTube for this reason instead of using VP9.
My computer doesn't have a hardware decoder for AV1 (as shown by "vainfo"), yet AV1 videos play perfectly fine on it, both within the browser (including on Youtube) and outside it. Playing the AV1 demo (https://demo.bitmovin.com/public/firefox/av1/) on the browser at its maximum resolution uses only around half of the CPU.
So, not an issue unless you're using hardware from 2015 or so? In which case you're unlikely watching a ton of 4k+ content anyway.
The machine does not feel slow to me. I have a fast SSD in it and lots of RAM so it is actually quite responsive. It just can't handle certain things like AV1.
There's barely any content though (possibly premium VODs on Netflix etc).
Bilibili (kinda like Chinese youtube) offers HEVC (and AV1) playback, if your browser supports it. Example: https://www.bilibili.com/video/BV1Q44y1372Q
In general it's kind of a moot point by now, just go with AV1.