Believe it or not, a lot of these features were already built into vanilla Xenforo. Trophies, featured threads, user title ranks, and the different username colours for usergroups are all just enabled by default.
Highlights, credits, stars, and referrals are all add-ons. These features are present in many other communities in their own way, but they might be new to everyone else here as, like you said, we're all used to a very barebones version of Xenforo.
I don't feel we've over gamified it yet, but I do feel we do need to make these features feel more like they're part of the forum rather than just add-ons, if you know what I mean. Like the stars, as an example. That was one that was a popular request on the other forum for years after the migration, and we're all pretty used to the idea of that. The star system here is based on a badges add-on that I adjusted to be a star system that works with trophies instead of just post count.
It does mean getting something like Sapphire Status isn't as simple as getting 100 posts and having a slightly aged account, but it does mean it discourages others from just gaming the system or inflating the post count for the sake of purchasing membership to sell. At the same time, I can acknowledge that the complication can be off-putting.
Even still, the star system feels a lot more like it's part of the forum than, let's say the credits system, which currently doesn't have much of a function here yet.
At the most, I do think we, or rather I should not add new add-ons right now because we do need to keep testing the ones we already have. I will admit that I am little excited being able to test so many of the ideas I couldn't implement for years, so I am adding things in a little fast.
I think in their present form, they're a little over-complicated, but we are also adjusting and testing things each day to balance it all out. Not all of features you see here today will be here even a month from now. A lot of this is just live testing because we're very limited on resources and funds at the moment, but it does mean everyone can give feedback on what they see.
Right now, we are trying to simplify the user post box to display less information, as right now, it looks quite cluttered and overwhelming.
If there's anything in particular you feel needs to be worked on even removed, definitely start a forum suggestions thread about it, I'm always open to making adjustments here, especially if it means taking the thought out of using different systems (again, credits is a good example of that).