On the one hand it's good to remember Manifest v2 is from a long long time ago, before Web Extensions API was a glimmering in anyone's eye. It was simply the chrome extension api back then.
It was powerful & capable. But it wasnt a standard, other than that it was by far the highest potential most capable most interesting user-agency extension on the planet by a good measure.
What's so fucking twisted is that we're undergoing "standardization" in v3 at the exact same moment Google is radically rewriting & reshaping the api to be far far far less capable.
It's hard to see a single win from any of the changes. After achieving world dominating success, the very last moment before standardization these chums have repealed a huge swarth of changes, all untested & unproven. It's amateur hour, just a sas ahit show right before standardization. devlarativeNetRequesr has some ostensibly good & virtuous advatanges, but it was obviously shit & deeply insufficient in the most woefully obvious of ways. Eliminating dynamic code was tacked on as a pro-security gimmick that didnt even remotely take technical interest & possibity into concerns: oh whoops we accidentally blew up userscript extensions, sorry, but you're all safe now.
This whole thing deeply deeply walks the line between vicious & evil farce & accidnetal fuckwittery. I still tend to give these folks the benefit of a doubt, that they simply lacked vision & respect & understanding & werent actively sabotaging & neutering the web like it certainly looks like.
That all said, v3 is actually the first proposed standard, seemingly sabotaged & crippled that it may be. So when you say this, I think, no, alas, everyone is for the first time trying to join up, just, alas, it's for misbegotten quite-possibly-sabotaged greatly de-fanged trash:
> As a developer of a browser supporting WebExtensionsAPI, the move to v3 is going to add so much complexity.