Mmm I know, its kinda frustrating because I honestly believe that the better you can assign hand ranges, the better poker player you are. I guess I'll keep learning by doing and loosing cash in the process
It's the most important concept in poker ainec.
Drop the number of your tables to like 4 or less and during each and every hand whether you're going to fold or not, ask yourself what range everyone in the hand might have. Speak out loud to yourself. For example, a TAG raises OTB against two nits. We know he's going to have a wide range, lots of suited connectors all pairs, but say this out loud to yourself and follow the progression of the hand.
Than as someone else said review your session after and look at every hand you played. Follow the reasoning in each hand and assign ranges, using pokerstove will help. You'll find a few leaks and maybe some things like "oh, I assigned such a range but then over estimated my
equity against it, next time I'll now that an X type hand has X% equity in this spot.
It's hard work but it will become naturalised. GL.