Definitely room for expansion here but it's still fun as is. 

Things to add would obviously be stuff like getting varying jump height working (I struggled to code that in another game too so I feel your pain, my solution was just spacing the platforms apart more in the end lol), a timer/score counter, some graphics and some sound.

Looking good though! No need to put yourself down, we're all here to learn :)

Even with the issues mentioned this was a fun game that had a single input so it deffo  ticked all the boxes!

For what it is, it's definitely enjoyable. Having the jump height be controllable would be fantastic as it is, but as Rob said, if you can't make something work, see if there's a way to work around it, such as increasing the platform gaps.

One minor issue I do have is that it takes a while to respawn currently.

This is definitely enjoyable, you mentioned the flaws you saw with it, but I think they could definitely, with the way the blocks show up, having a constant jump makes the game very difficult to make certain jumps which is great. I think the only thing would be for a score system,  just so we could see how far we've gotten.

Honestly still a fine little game despite the issues you mention, one thing you could try is leaning into your perceived 'mistakes'. If you can't change the jump height, make the gaps between platforms bigger! There's no need to be too hard on yourself, whether you were serious or not.