Computer memory performance is a hierarchy and a series of trade-offs.
Main memory usage is used for app and data, and for I/O caching, and for avoiding a trip through (higher latency) main storage for (whatever), as well main memory used for graphics processing, and for ML/LLMs.
Is main storage faster than it has been? Yes. It’s now running at DDR3 SDRAM main memory speeds from ~fifteen years ago, with current Apple M5-era SSDs are mid-range DDR3 SDRAM bandwidth. Can that bandwidth mask insufficient main memory? Yes.
I’d absolutely aim higher than 8 GB, particularly if planning on running the Mac until it falls off of macOS support.
PS: The lack of ”free” main memory is often misrepresented as a problem by sketchy vendors seeking to sell their “cleaner” apps, too. Alas, “free” memory is wasted memory, and macOS seeks to use whatever is available. Clearing that memory can mean added trips through main storage or through app processing to regenerate the data or whatever (bandwidth and latency incurred), which in aggregate slows things. But free memory.