Look, game design advice - it seems your idea of raising difficulty seems to be limiting the player. Throughout the game you need to wait as the screen scrolls, then there are the orange blocks - look, game design advice - this just doesn't feel right in a video game. In general, it's better to add multiple systems and let player come up with interesting solutions to problems you create. And this applies to every game, look even at classics like Megaman - you can pick many paths through the game, and sometimes even through the levels themselves, fight bosses in different order, you decide what weapons and items you want to acquire when, and how and when to use them limited only by weapon ammo system - even when there were autoscroller levels they were few and far in between, a break from the more open rest of the levels. Same goes for other classics like Zelda or Metroid, just even harder - and hell, even Super Mario Bros had more gameplay depth between different powerups radically changing gameplay, secrets and warp zones, ability to play as Luigi in Lost Levels and generally deciding whether to go fast or slowly, and whether to try to engage enemies and risk getting hit in the process, or try to avoid them and risk getting hit in the back - reflected in game design, every castle boss could be defeated by being fireballed to death or by being dodged and taking the axe. Worst levels in Super Mario Bros? Water levels where you were usually unarmed and in constant danger, and you didn't have the tools to deal with that danger anymore.
Here, your idea of creating a challenge is to give player very little tools to deal with challenges ahead, and then at certain points limit player's options even more (make him wait for the orange blocks to touch lava, place enemies in a way that you can't skip them, make player guess what's ahead, and so on.) The only emotion it creates is frustration - and if you're intentionally trying to create a game about frustration, like maker of VVVVVV did, then it's fine. But I don't feel like that was the goal here, you were trying to create "challenging but fun" game and simply missed the mark.
It's especially annoying since some stuff is done well - introduction of new gameplay mechanics is done well and in self-explanatory way, and visual style is pretty neat, feeling faithful to the NES aesthetic. Controls are tight, music is good - just work on our design skills and you have potential to create some great games.