Relatively trivial UI features are ignored in an effort to force conformity

The downvotes on this answer appear to be an objection to making the sort by Age the default. That's from other Meta users. The question itself has net positive votes, which suggests Meta users would like to see the option to sort by Age, but to keep the default as sort by Score. That doesn't seem like a no, just users expressing support for the idea and their opinion on what the default should be.

We live in a world where there are many types of users, there are almost as many use cases

I definitely agree with this. I'm in favour of customisation. I'd like to see the option to change the default sort order per user per site, so I can set it to my preferred sort by Score on sites that are about getting answers to questions, and my preferred sort by Active on Code Golf and here on Meta, so I can see the latest answers and edits in an ongoing competition or Meta discussion. That would then leave me free to switch temporarily to sort by Age when I want to go back and review the history in order. I don't know if this customisation has been requested anywhere yet.

I have recently raised a large number of bugs and feature requests on Meta and I like the fact that the community can vote to show which ones are more important to them, to help prioritise work. As the work will be done by a small team of unpaid volunteers I didn't expect to see any changes in the short term, just to raise the requests so that prioritisation could be done for the future. However, I've already seen several changes implemented, which makes me feel it's worth putting the time into raising things.

Not all of my Meta posts have a good response - I have a mixture of upvotes, downvotes, and some with no votes at all. Having the community indicate which of my posts are worth prioritising means I don't need to overthink things and can just raise everything I think of, without trying to guess if other people will want the same thing. I like the way this works.

I haven't seen an objection to making changes. Comments from Codidact staff on my posts have been positive and seem interested in finding out what is wanted. They are volunteering and don't have full time hours available. It seems like they are making changes as they find the time, rather than being controlling.

As a specific example, I received a comment that was positive about adding in an extra sorting button in another context (about sorting search results - seems very similar to this feature request).

In addition to the requests I've raised and seen implemented quickly, I can also see others have been added to the GitHub issues list and are being tagged and prioritised.

The priority order settled on is never going to please everyone (we all have different things that are important to us) but as it's open source anyone is free to work on something that is not at the top of the priority list. I don't know the Ruby programming language so I haven't been able to work on things I'd like to see implemented, but I did raise a very simple pull request for a typo and it was accepted quickly despite not being high priority.

No one has said no to adding this sort by Age button, and as you point out it is already implemented for the posts list so most of the code needed already exists. So if you don't want to wait for it to work its way up the priority list it might be something you can do yourself without necessarily needing to be very familiar with Ruby.