Hehe... nick chosen for a variety of reasons :)
I'm going to point out that storing user IDs and such in the payload is perfectly acceptable, and one possible means of transporting a user id around rather than as part of a url path, query string, etc. Because the payload is typically meant to be readable, there should never be any sensitive data like password info added to it. Note that while JWTs are used for authentication typically, thru are also used as a means of secure message passing.
Anyway, proper use of a technology comes down to developer awareness, but I would hope that the developer implementing any means of security would do some research into doing it properly. We can't blame the tool for being used incorrectly :) Perhaps the problem in this case is a lack of sufficient proper documentation? Can't say I've found lack of docs to be a problem, but I guess people's mileage differs.
As for my points 3 and 4, I did mention that they included a DB lookup. I don't believe I've ever read anything that claims that it prevents a DB hit. In fact, this[1] page states that they help to prevent more than 1 DB hit for user info.
However, what I was trying to allude to in my previous comment was that you can store the bare minimum info of your users in a cache. This cache can be used during the validation of the token (and even with token generation) , which prevents a db lookup. Since the data in the cache should contain data that rarely changes (should only typically be updated on password change, or when any of the details used in the payload of the token changes) , management and maintenance of your user cache is simpler.
Specifically on point 4, what I was suggesting is that if you are planning on using something like HMAC as the algorithm for signing, then the signing and validation steps of the token can include the password hash or similar unique value for the user in addition to whatever key is provided.
In addition, if your tech team has access to your production DB, you have a concern when anyone leaves anyway, regardless of what authentication method you are using. So not really something specific to JWT. In the case of JWT and using HMAC for example, I would have my production key stored in the prod environment only.
I will say that changing a key is a real concern, if your key does become compromised... but it is possible with a bit of thinking upfront about it. I've successfully implemented something like this previously.
Again, it's not the right tool for every circumstance, but when used in the right circumstance and in the correct way, I don't find most of your post to be relevant (meant with good intentions and I'm not trying to be provocative).
Perhaps a quick read through the Wikipedia page [0] on the topic, but more importantly, the JWT IO page [1] on the matter provides usage and implementation guidelines, as well as confirms some of what I've mentioned previously.
[0]: https://en.m.wikipedia.org/wiki/JSON_Web_Token
[1]: https://jwt.io/introduction/