The transformations do kinda make the game way easier in parts but you can see what they were going for because some of the bosses sorta require you to have a certain transformation or weapon. I recently played through this for the first time a few weeks ago on that new 150 in 1 cart think I got to like the end of the fourth world or beginning of the fifth it gets sorta cheap towards the end so I gave up on it. Didn't even realize it has 2 player co-op I'll have to give that a shot that's pretty rare for a NES platformer.

An underrated game that this is really similar to is Totally Rad which has a better take on the transformation concept although its a bit more of a run and gun. NES prices are strange I was going to list totally rad as a really cheap alternative to this but I looked it up before posting and it's now a $20 game I paid a little over $5-$7 just like a year or two ago.