Comment by opan

I did similar as a kid, weird random typing, mostly left hand, thumb used for some of the letters, etc. If you're willing to dedicate 2-4 weeks of fully immersed proper typing, you can definitely undo the old habits. Takes a bit longer to regain your old speeds, but it's mainly the very beginning that is frustrating. Whether that's worth it is hard to say. I use both shift keys now, and a split ergonomic keyboard. The numrow is easier to hit accurately as I have internalized the placement as well as the rows of letters after a lot more typing practice (columnar stagger rather than row stagger also helps, I think, I slide my fingers straight up and know which numbers are there).