No, it actually is due to weird hitboxes and enemies being spammed senselessly.... with the high HP trying to take them out
"Not difficult"? You must be playing a different game or something cause even the lowest difficulty is a chore
I will not deny that the game has some very weird hitboxes and getting spammed. However, I don't see 4-6 hits being high HP. Each strike on them knocks them back(except for vents), and you can still hit them when they are "knocked down" and "knocked back" (although you need to crouch attack them when they are knocked down and the tentacle man, dogs, and low flying snake heads can only be attacked by crouch attacks) except for those vents but they can avoided by rolling, although be prepared to be grabbed by something else..... which is a terrible decision of the dev that the roll and jump attacks doesn't provide you collision i-frames (rolling only gives you attack i-frames from vents since the vent themselves doesn't have collision hitboxes).
Also, no. I didn't play the game extensively. I only played it for 1 run, just to unlock the gallery, which is like 20-30 minutes. However, I have played those old flash games like the Angel Girl, or Karate Girl, or Witch Girl, or the one Asagi looking one. To be honest, those games have a lot more faster enemies than the ones here.