You definitely need more RAM. You'll see a great performance increase, and then be very happy with your new Mini.
With every new release of macOS the OS itself requires more ram. This is why many people say their computer has slowed down over time. It's due to OS updates. 8GB is teetering on barely enough to run the OS, let alone any app you want to run. On my Mini Mojave uses over 7GB.
I'm running the new Mini with 32GB and here's a screen shot of memory usage with
nothing running but the OS.
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