1. You can run any unsigned or unnotarized software from any developer by right-clicking the app, selecting "Open", and then click the "open" button in the scary warning. It's really simple. I wish people would stop pretending like it was really hard to run unsigned software.
2. Apple does not "curate" or "review" software distributed outside the Mac app store. The notarisation process runs some automated malware checks, and that's it. The goal is to block malware, not to limit the content you put on your computer.
3. Notarisation takes less than ten minutes. It's easy to automate it, and you can also do it manually if you want. You can staple the notarisation ticket to the app, but you don't have to. MacOS will look up the ticket via a webservice if you don't staple it. The documentation sucks, but that's the only bad thing you can say about it.
4. Apple does review stuff you submit to the Mac app store, but fortunately it's entirely optional to submit stuff to the Mac app store, there's nothing stopping you from releasing software outside the app store without any review.
5. Apple did end support for 32bit apps, which sucks, and I don't have anything good to say about that.