All of these invented system carry their own pros and cons, but the aversion to "junk associations" is an extremely common misconception in my opinion (one that I held for quite a while as well). Many will argue that relative to your total cognitive power the cost is virtually zero but I don't think the discussion needs to go that way, and here's why: like anything, the beginner has to force everything. You put in the effort consciously because you recognize it as a step in some process. If the technique remains a novelty, then that's where you'll stay. Your associations may get ever more clever, simpler, faster, etc. But when you start to apply it constantly in your work and in everything else that you do, soon the technique simply fades into the background until at some point it might as well have disappeared. It's like math or spelling as a child, where you have to learn step by step what is and what isn't until it clicks, and then the why no longer matters. You add two numbers because that's the way it works– you don't have to convince yourself. As your memory progresses you the junk associations will fade out and stronger associations predominate, because they're relevant and you want to remember relevant things.

Edit: this is especially relevant to the "read me a list and I'll repeat it forwards, backwards, or in any order you call out" party trick.