I mean, I do projects on mine too. Without OP describing what the projects are; you're assuming they are CPU-bound.
Speaking of my projects - the RPi is perfectly capable of working as a web crawler (at a page rate that may surprise you) as well as a media download client & transcoder (again, simultaneously transcoding a number of streams that may surprise you).
Yes, the pi is perfectly fine for many projects, and in fact I have a couple of old pi's (even the original pi 1!) running tasks, such as listening sensors over bluetooth, pihole as DNS server etc.
The reason I prefer mini-pc's over pi is the x86 architecture and possibility to add more RAM. For maximum flexibility, I mostly run my self-hosted services inside virtual machines that I manage with Proxmox, and pi isn't ideal for that. Admittedly I found even the mini-pc's too limited due to lack of space/pcie slots for a GPU, and ended up with a custom desktop build. That allows me to experiment with stuff like self-hosted AI, and game remotely. Support for ECC RAM and more SSD's was a big plus too.
So, indeed it all depends on what and how much you want to do with the machines.
It's fine that it's enough for you and I applaud you. I was also not only talking about CPU but also IOPs some of us have more demand on what we call a server. I don't understand how you can be so defensive about a piece of hardware it's actually rather concerning and my zero w 2 does have problems with FullHD streams with high bitrates. It doesn't even have the io bandwidth to push more than one stream.
Speaking of my projects - the RPi is perfectly capable of working as a web crawler (at a page rate that may surprise you) as well as a media download client & transcoder (again, simultaneously transcoding a number of streams that may surprise you).