It seems to me that there are three different questions here. And I'm sort of agnostic about all of them.
The first question is whether we need more moderation to counter rudeness or other sorts of dissatisfaction with the site. I don't generally find this site particularly rude or unpleasant. Like anyone else, I sometimes encounter behaviour that makes me wince. But that's life. I know nothing about moderation action, whether directed at well-known or not well-known users.
Anyway, I really doubt that we need more moderation, as such. Mostly, I think, the site community as a whole manages to make its feelings reasonably clear, as it did in fact on this thread. I suppose we can all help the moderators work efficiently by flagging things for their attention iff they really need their attention.
I'm afraid I incline to the fatalistic view that if somewhere needs constant policing to avoid falling into antisocial rancour, then the game is up. I don't for a moment think we are in that position. But if we were ... I don't think more, or more aggressive, moderation would help us.
More diverse moderators?
A second question is whether it would be a good idea to have a moderation team that represents a more diverse range of backgrounds, points of view or (prosaically) time zones. I'm always in favour of diversity in leadership, because I find from my own practical experience that it helps encourage a diverse community. But, for all that, I rather doubt that in this particular case that would justify appointing extra mods. Why? Because -- and I think this is a good thing -- I don't think the mods here function as "leaders"; I don't think that they "set the tone" or dominate the discussion; I find that they largely disappear into the background, and I think they deserve credit for doing so. So in this particular case I doubt that having a wider range of moderators would have much impact. I don't know when elections are held. I'd certainly like to encourage as wide a range of candidates as possible when they are. But that's a different thing.
Ennui and the end of days?
Finally, I detect in the question a certain sense that the site is currently a bit "below par", compared perhaps to the early days, with people leaving and so forth. Well, I have mixed feelings. I don't think it's surprising to find people leaving. There comes a point, perhaps, when people have "had enough", quite naturally; when the questions start to get dull, and the most dedicated expert wants to move on. That's not necessarily unhealthy: it can make room for new folk, which is a good thing. If you've been around here for a long while, I suppose it's easy to find that most of the most interesting questions have been asked and answered, and hunting down duplicates or answering very specific questions can get tiresome. I don't think we should be worried if people move on.
There probably are some basic defects, almost genetic defects, in the structure of this site. After a certain point, when the "big, common" issues have been addressed in canonical answers, there may not be all that much to do, and it's maybe natural that the site becomes dominated by sometimes rather tedious issues. Those issues matter for the users who post questions about them. They may be interesting enough for intermediate users to be willing to spend time on. But I think it's sort of inevitable that real experts are going to turn their attention elsewhere, and probably it's healthy for them and for the site that they do.
Is there anything we could do?
Yes. As always. We watch our own behaviour. If we don't like rudeness, let's make sure we are not rude. If we want to encourage questions, let's be encouraging. If we want to encourage real understanding of TeX, let's post answers that explain. If we want to discourage DIFM questions, let's resist the temptation to Do It For Them. If we want to encourage new answerers, let old-timers be generous in not rushing to answer questions, and let's all be generous in upvoting carefully done questions and answers. Let's resolve not to close early and often. Let's resolve not to ask for MWEs on questions we have no intention of answering. All those things, which we all probably know. Moderators cannot, however dedicated, to that for us.