I love the game and think it's super fun, but it feels like it's kind of broken and not really an idle game anymore. Starting at the highest reached checkpoint combined with needing a manual restart on each horde death meals it is incredibly difficult to get over difficulty humps, or at the least very annoying to do so.
Combined with how Mutation points are limited at five, meaning you have catch and reset as soon as possible to effectively not lose out on points, it means you have to keep active focus on the game the whole time for it to progress, so not really idle so much as slow and frustrating.
I think removing the limit on Mutation points and the manual reset for each horde death would solve a lot. Starting each run from the latest checkpoint can be a problem as well, since it can effectively softlock you.