Why katakana makes my brain go slow

リソンシツ

Kinda like the English 1,l,I... except it's all in the same "case". Script g and q might be a more fitting example.

They're different, obviously, but similar enough to need to slow down in order to process. Especially 「ソ」 because I never see it used.

Also: フワウラ、ヲヨコユ、テチ (and more...)
Not nearly at bad, but all together they make for slow learning.