H.264 will become the "mp3" of video I think. Universally supported, and the pstents will run out micj sooner than the newer formats.

I think you’re right - for a lot of people it was the first to hit the “good enough” threshold: going from MPEG 1/2 to the various Windows Media / Real / QuickTime codecs you saw very noticeable improvements in playback quality with each new release, especially in things like high motion scenes or with sharp borders.

That didn’t stop, of course, but I generally don’t notice the improvements if I’m not looking for them. Someone with a 4K or better home theater will 100% benefit from newer codecs’ many improvements on all those extra pixels but if you’re the other 95% of people watching on a phone or tablet, lower-end TV with the underpowered SoC the manufacturer could get for $15, etc. you probably won’t notice much difference and convenience will win out for years longer.

Reencoding will cumulate H264 artifacts with H265 artifacts (and psychovisual optimization for one with psychovisual optimization for the other). Unless you reencode from source don't do that.

i appreciate your concern :) but honestly, is that a practical problem, or a theoretical one? the end result was fine to watch in our case. (and upload itself wasn't of great quality anyway)

It can be a practical problem depending on the source: if you're moving from a relatively higher-resolution / less-compressed video it won't be noticeable but if you're starting from video which has already been compressed fairly aggressively it can be fairly noticeable.

One area where this can be important to remember is when comparing codecs: a fair number of people will make the mistake where they'll take a relatively heavily compressed video, recompress it with something else, and get a size reduction which is a lot more dramatic than what you'd get if you compared both codecs starting from a source video which has most of the original information.