2012 Mac Mini getting annoyingly slow.

[rich in distress]

Grumpy guy, I respectfully disagree.
Re: RAM, not how much you use, but how fast you switch... i.e. good codIng.
You see 8gb getting filled, because you use 8gb.
There's no good in any amount of RAM that is not used.

Edit: Also, new or old accounts will be equally affected by malware or HD failure.