As a kid with no cash but a lot of passion, I spent months cobbling together a fully working version of Photoshop 7 (pre-CS days) from various files extracted from free demo and upgrade installers. Technically did nothing illegal and ran that single version for a good 18 years across various PCs, eventually powering a large media company's output with it (in fact there's a very good chance anyone reading this will have seen some of my Photoshop work given the reach of that company).
The main reason I never upgraded was that it was FAST, and until Adobe started rolling out AI features around 2020 there were almost no notable additions made to Photoshop other than new versions seemingly getting slower and arguably uglier. To this day I'll still occasionally boot up the old Photoshop 7 if I don't need to use content-aware fill, and I'll marvel at how zippy it feels.
I spent a lot of time in a… not-quite-legitimate version of PS 7 too. Feels almost like a rite of passage for many of us of a certain age.
And yeah, 7 was quite efficient and zippy, basically just 6 with a few new features and compatibility with newer OSes (first version to run natively on OS X for example). Ran it on a 400Mhz G3 without issue, which would be futile to even attempt with modern versions.