I also got the Corgi Engine in one special offer sale, a while ago. It looked very custom, no Unity physics but its own system etc. That’s a perfectly reasonable approach for many types of platformers, “classic” ones and especially considering that Unity’s 2D features are fairly recent. However that approach imposes a dilemma: you can use it right away and it’s fairly easy, but once you want to step out of that box, it’s much harder because you need a good grasp of coding to understand how they build it (so you can adapt it).