Yes, some projects take more time - some because they are difficult, some because they are boring. Worst are those nearly finished where you "only" need some more steps ;)
If the strap is too long you could shorten it with a wide brooch, perhaps you could even crochet something that matches the bag. That wouldn't shorten it permanently but you could change it as you need it.
I decided to just tie a knot on the strap. Lol. I think I might look for a brooch to make the knot a bit more stylish.