As hinted with the Finder comment, "Spotlight" is behind much more than the command-space search box. I don't know what the Siri services might do other than Siri itself, but wouldn't shock me if they were involved in things like Shortcuts and Control Center widgets. I understand thinking things you don't use are simply a "waste of CPU and storage space", but this reads like the kind of posts I used to see in the Windows XP era where people would open Task Manager and kill random processes they didn't understand. Best to make a little more effort to understand what the OS is doing before taking a scalpel to it. Or if you'd rather not, there's always OpenBSD (being serious here, it's pretty cool).
Howard Oakley has made more effort to understand what macOS is doing (and blog about it) than practically anyone else ever.
If some process is going to take hours of cpu time, it should be opt in. At a minimum I’d like to be able to turn the bloody things off if I don’t want them.
I run cpu usage meters in my menu bar. The efficiency cores always seem busy doing one thing or another on modern macOS. It feels like Apple treats my e-cores as a playground for stupid features that their developers want a lot more than I do - like photoanalysisd, or file indexing to power spotlight, that hasn’t worked how I want it to for a decade.
I have a Linux workstation, and the difference in responsiveness is incredible. Linux feels like a breath of fresh air. On a technical level, my workstation cpu is barely any faster. But it idles at 0%. Whenever I issue a command, I feel like the computer has been waiting for me and then it springs to action immediately.
To your point, I don’t care why these random processes are using all my cpu. I just want them to stop. I paid good money for my Apple laptop. The computer is for me. I didn’t pay all that money so some Apple engineer can vomit all over with their crappy, inefficient code.