I mostly relied on mnemonics for items that felt unintuitive to me and which I had no previous experience of seeing as part of other words. So, I’ve relied a lot on the example words for memorization of the readings, rather than the mnemonics. But, from lv 40+ I also mostly used the Keisei script to recognize radical components that gives you the reading.
Again, that means basically ignoring the mnemonic.
At other times, I would write my own if I felt inspired somehow.
Basically, if you wanna go fast through lessons, not using the mnemonics is defo faster.
But, as I said, whenever I felt like the mnemonics were the best way to memorize something, I would read them in full.