Yes, and still am. Not really active anymore since I'm busy with other things. I don't read much, but I can read a book, albeit slow and with much difficulty. Writing I do even less, and handwriting I never really did apart from tests and filling in forms. Speaking and listening I do every day. After a while I just decided to not focus really much on handwriting because it easily takes the most effort for something I actually barely use.

I've played a bit with memory palaces for fun and found them to be effective, but really not for Chinese Characters. I mostly used my own flashcards with Anki. I used pictures and tone colored characters to help. That worked fine, but making the flashcards also took a lot of time so it wasn't really perfect either. Having many synonyms also complicates the whole ordeal. But overall spaced repetition really, really helps with managing lots of vocabulary. You can have a deck of several thousands of words without too many issues. If you find words hard to remember it's also OK to just delete them (Anki also helps with this by automatically labeling cards you often fail as leech).

The mnemonics I use are the "build in" ones in the characters, maybe you already do this by yourself and actively learning them won't change too much. Nearly all characters have some meaning and/or pronunciation component hidden in them which can help you remembering them, or guessing their meaning or sound when you first encounter them.

I don't really think about radicals since those are just arbitrarily chosen components used only for paper dictionaries (and who wants to use those in the age of smartphones...). Some random examples of interesting components: 疒, is a character that is not used anymore (I think) but it means disease and if any character has this component you can be very sure it's some kind of disease.

月 is a tricky one. It's moon and it often really doesn't make sense in words until you know that 肉 is often corrupted into 月. The 月 in 脑 doesn't mean moon but meat/flesh.

Some characters change depending on where they appear as components: 水/氵, 人/亻.

I like to use the Outlier Linguistic Dictionary on Pleco for looking up how characters are build up and see if it can help me remembering the character. I find little stories help me to remember words/characters. A character I forgot how to write and just looked up: 虹 (rainbow). It' made of the component snake/insect/worm because the ancient Chinese thought it looked like a snake in the sky. 工 is there for sound because gong/hong sound similar. Or 取 (take/get/fetch), it's literally a hand taking an ear.

I don't think mnemonics is the One Easy Trick that will make your routine 10x more efficient, but depending on how you learn now it could really boost your efficiency. If you're not using any form of spaced repetition yet I think that really could be it.