drop-in upgrade or whole new platform: what did you do?

so annoyed rn maybe a weird question, but how do u actually feel a CPU upgrade? i hear people say their old laptop chip was 'holding them back', but my PC still feels fine for streaming while gaming... i'm trying to figure out if i'm missing something or if the upgrade itch is just marketing. Is there a simple test i can do to see if teh CPU is actually the limit? i'd rather measure it than trust my gut or someone's review chart. any ideas??