I've been running a UDM and UDMP for years, and have literally never run into any of those issues, despite having a somewhat complex network (for a home network anyway).
It runs 24/7 and only needs reboots when a software update requires it. Multiple VLANs, road warrior VPN. I run a site to site VPN between my UDMP at home and UDM at my summerhouse, and that has been rock solid as well.
In the latest EA version of the software, there is also some support for Wireguard (though UI's Teleport). I'm not sure if "raw" Wireguard is available (yet).
Latest version also implements policy based routing.
I’m in the latest stable version, as I updated after an outage last week where the controller was crashed.
The variability in user satisfaction suggests some sort of hardware issue or bugginess that hits a small portion of users.
The APs are good and the switches too in my experience. However the UDM-P is a troubled device. It’s buggy, things break or stop working and it loses its config every so often. The form factor is very compelling and the concept is great.
I’d pay more if the software quality were better.