Stop looking at the memory consumption number and look at memory pressure.
Basically: you don't know what you're looking at (along with plenty of other people). You are witnessing disk cache.
This is why the memory pressure graph exists: because memory consumption is not an indication of memory shortage on a modern machine (i.e., once running an OS from the past 30 years or so that uses memory effectively).
Additionally, looking at process size in Activity monitor doesn't really show you how much RAM it is actually using, it shows you a virtual address space it is using which may or may not map to real memory on your machine.
Basically...
FREE MEMORY LOW BLOAT OS DERP
is outdated thinking from the days of DOS, AmigaOS, System 7 and the like.
This is why Apple has had a memory pressure graph for the past decade - to help people understand what is actually going on without needing a degree in computer systems engineering an memory management - and even if so qualified, manually looking into various metrics to calculate it. The pressure graph does it for you.
The above applies to Windows 2000 onward, Linux, MacOS the BSDs, etc.