DarkMode I use a Google Pixel 8 since 2 years without any problems, I am not aware of any problems with overheating, software bugs, etc, even with the stock OS, I have not encountered any of these issues.
It is important to bear in mind that absolutely all electronic devices can have bugs, and that negative comments tend to be amplified on the Internet because only those who have problems come forward to complain, while users who do not have these problems remain largely silent, and I would wager that these users constitute the majority of all users.
I would probably go for a Pixel 9a if I were starting out, but the Pixel 8 works great for me, is MTE compatible, and will receive security updates until 2030. If you can get it at a good price secondhand, or even new, it's a good deal.