I am looking at the notes you provided from the video, and will respond by each point.
1. I think it's fine to start with a concept and pick whatever abilities fit. I don't think this is against the idea of optimization.
2. I don't think death is objectively bad, but it's up to each player to be okay with ideas being thrown away or not. If all of this "non-optimization" stuff is for the sake of RP, wouldn't it be nice to stick around and keep doing it?
3. HARD NO. The challenge aspect is dependent on the DM. An optimized character is good at "their thing," when does not being challenged come in? My fire optimized build isn't going to overcome a physical challenge. I don't think it's normally possible for any DnD character to be the "best" more than a few things, much less everything, to the point that nothing challenges them. And beyond that, this makes some big assumptions about the role of challenge in a game or story, or how it manifests, etc. This point may just be made for video fluff, but if sincere, this is just ignorant.
4. I disagree. No matter what you play, you can demean any character to "repetitive, boring attacks." Nothing about optimization inherently forbids creative use of the character's tools.
5. Maybe some players like this are trying to "win" the game, but I personally wouldn't make a generalization about why and how people are having fun. I do it because I am trying to execute a concept-- the gameplay and the RP are codependent in many ways, including this. What if being reliable in my combat role is fun? What if suboptimal tactics just get in the way of reaching my narrative and gameplay goals? Hell, if I'm being entrusted with responsibilities to the world's characters, should I not try and make effective decisions in universe?
I don't like anti-optimizers, because there's not really any good reason to take on that mantle, to me. Let people play the game.
