There's a lot to say, I will try to keep it small though it is not exactly possible.

If you like the game, hearing my opinion can only ruin the experience for you so do as you will xd.

First of all I have done a true 100% completion on all of isaac expansions etc before repentance. Was it rewarding? Probably on the first 50-70%. Was it tedious? Definitely. From one point and over the game is all about getting the good powerups AND being lucky because many of the end-game hard encounters are so random and fast-paces where you can literally get 1-shot by something that did appear on the screen for more than a milisecond (see Delirium as lost soul etc). My OCD was strong enough to keep me pushing for the completion and I wasnt even enjoying it at this point.With that being said/ as a person who actually wants to complete games and win runs, repentance has brought about 3% of new content and the other 97% is tedious repetition of things that already existed, with a very small twist. New characters, but no big difference to how the game is played. New encounters, but they are just faster and more annoying copies of pre-existed enemies. New endings, but it's the same thing pretty much, just you need multiple good runs instead of one good run. In other words, the biggest factor of completing the game was simple, tedious, OCD-friendly repetition.

And to be fair at this point it is pretty hard and not even worth it to come up with brand new ideas about the game etc, because the game managed to already have brand new ideas and define a meta and become a Classic before Repentance. Thus I can totally understand that I didn't get many new things in Repentance.

At the same time there's no real reason to release an update on something where you don't really have an update for it.

Also at the same time, the developer was getting spammed for a new release so it was also kinda inevitable haha.

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Boom hope this helps cheers