This is my main computer. Last month I upgraded to an OWC SSD and did maintenance on the macbook (new battery, new paste, new foot pads, general cleaning). I went from the original 256 GB to a 1TB SSD bought from OWC along with the enclosure to keep the original as a backup. I regret it since I sacrificed speed for space. But it still works. I stayed with Big Sur because of stability and compatibility with hardware/software (printers, scanners). I don't do video/audio editing, so maybe that's why I don't notice it's an 8 year old computer. If your usage is light, I don't think you'll have problems and you can still squeeze a couple of years of this machine, which is great if you're the type of person who doesn't like throwing away machines that still work.
One thing I wish I had is a fingerprint reader, though. It's a drag to manually enter passwords.
BTW, as a light user I bought a PRO with 16Gb directly from Apple because I knew it would last about 10 years, since my last mac was not a pro and still worked for about 8 years. I probably wouldn't have been able to add the 1TB SSD with the standard 8GB of RAM.