I've been using an older mac mini with sequoia, and have not upgraded the OS because that will break a whole bunch of plugins and accessory software that I don't want to buy needless upgrades for. Like you said, it's not broken, and probably functioning just as well as any newer stuff.
Been using Reaper DAW for a few years with no complaints. It even plays well with most of my old Cubase vst plugins, CLAP, LV2, etc.