I prefer F-Droid (using the Droid-ify front end) but I've used Obtainium for a few things. Definitely a useful tool, even though it's not as user friendly as using Droid-ify.
Fdroid is the same as the Google Play. They centralize everything in the decisions of the few at the top of the group. If they don't like what the app dev is saying, the app doesn't get listed.
True, but the F-Droid app itself allows you to add other repos even if their default repo is problematic. Droid-ify has some others baked in by default, such as IzzyOnDroid. As long as I'm able to fall back on Obtainium, it's all good by me to use F-Droid, but that's just the way I view it.