I study the mnemonics, yet find that over time I recall the kanji/vocab without even thinking about the mnemonic (which is the ideal, where the kanji/word itself has become ingrained purely as a visual pattern) - but! if it doesn’t come automatically I think about the kanji(s) and the mnemonic(s) for that item, which in turn helps solidify the meaning.
The mnemonics really do serve a purpose, and using either the inbuilt or your own custom ones are seriously worthwhile. I’ve started doing a lot of reading lately, and when I can’t grok a phrase quickly/effortlessly, I can often work it out by dredging up the mnemonic - otherwise it would mean resorting to a dictionary every time I cannot recall a word that I’ve already studied.
I previously did anki daily for months without mnemonics - and forgot almost all of them once some time had passed, the neural connections were just too low for visually similar and higher stroke characters.
Keep in mind that WK goes by stroke count, so the lower levels are easier for visual recognition since they’re simpler and more distinct. Once you have some high stroke similar kanji, and the only difference is a mouth radical vs a sun radical (among 4 other radicals) - the mnemonic will save you.