Life is too short to learn all things. Pick what you want to learn and use that.
I do use assembly, but I'm just a gigantic sucker for banging the hardware of retro computers directly. Looking at what you managed to do in Blitz in such a short time, I'm kind of envious. Sure, Blitz is slower - but you got a lot done and it all works well enough.
IMHO, assembly is something you should only use if you either need it (i.e. you can't manage to get the speed you want without it and you've done all you can to make the non-assembly program itself as efficient as you can), or want to use it. IIRC, Blitz actually offers a nice compromise here - you can include inline assembly easily if you want too. But you don't need to
