I just want developers to consider their deployment environment and maybe generate and include more capable, POSIX BB instead of just choosing the smallest and most useless.
This is completely fair, but the only example you gave to show this was about regexp in OpenWRT, and it seems from the other comments like there are several ways to go about doing this. You mentioned half of your RAM being free, but on the flip side of that, something with half as much RAM or less would be struggling a lot more. Admittedly I don't know much about OpenWRT but routers aren't exactly known for being powerful systems, so to me this seems like a perfect use case for a leaner set of utilities.
To your other point, languages like Python and Lua might not technically be everywhere but it they are common enough and simple enough to learn that you really are holding yourself back by avoiding them. Lua in particular is used by a lot of Linux projects (e.g. Neovim and Awesome WM are the most recent that I've used but there are tons of others) because of how easy it is to embed a configuration/plugin API into existing codebases.
Tldr; you're being dissed because the only example you gave about BusyBox being overused is (on the surface at least) a valid use case with easy solutions that you seem to be intentionally ignoring.