This hack, besides from finishing after around 30 minutes, is very very repetitive. The castle is an example I could mention: after the rooms of enemies (which could make you get stuck if you're not cautious), the design is very repetitive, with same-y sections and the likes. The whole design is overall extremly linear and unfun: not that being linear is not fun, but here the path took for design is "do a straight field filled with enemies" pretty much.
Aesthetics are pretty mediocre. While the additions look nice, the way you placed them in levels and the combinations with the BG (which most of the times feels too empty) is very poor. There are also some weird palettes going on here and there (the rocks in the first level, the ? blocks in the castle), which make me feel like it was all thrown together in a few minutes. Could've been much better.
The only issue I found here is that the hack breaks due to music on accurate emulators. I already mentioned also the fact that the rooms of enemies could get you stuck if you don't watch out.
Obvious title problems aside (in literally EVERY INSTANCE OF IT), this hack wasn't too bad. Levels were rather repetitive at points (including constant use of shell kickers) and every now and then they were rather flat and uninspired (the time lift section being the most obvious point >_>), but there's nothing too fatally wrong with this hack that I could legitimately call "terrible". It's decent, but generic.
1) The music in Mushroom Kingdom 1 is atrocious and repetitive, with its constant @7s blaring the whole time you play it. Also on the topic of music, Mushroom Kingdom 2's music didn't loop for some indiscernible reason.
2) Fadeout problems in Mushroom Kingdom 2 and 4.
3) One particular kill room in the castle is straight up unfair between the spiny egg ambush and the fact that if you don't have a flower, you probably won't survive the room.
As a side note, I'm rather surprised that the music didn't crash in SNES9x, besides randomly stopping. Or maybe I just got lucky and other people will have the music crash. I dunno.