It's a difficult battle in many teams where some people will just go overboard for multiple reasons, usually in this order: fun, fear of being seen as short-sighted and/or promotions. It mainly happens in big orgs and your examples definitely fit the bill although I haven't worked there specifically. I'm not that old (very late 20s) but I've seen overengineer code (or infra) ending in the trash so many times... many people could see it coming and warned about it, yet it still happened.
I usually try to support the opposite idea by bringing agile to the table. Agile doesn't say "please don't overengineer" but "this can change a lot in a couple sprints, requirements may be different, there are more (or none anymore) use cases now" and hence why to spend so many resources doing something that not only doesn't cover all potential unknown use cases but also adds overhead when reading the code for no benefit. For some teams this has clicked very well. Appropriate agile training can help a lot.
However it doesn't always work and if the person(s) doing this have higher ups backing it up (even if unintentionally) you're fighting the wrong battle. If you can't change it, move teams or to a company where money is a bit tighter and/or where these behaviours aren't tolerated - in other words, where things needs to get done and there's no time for experimenting with things that most likely won't yield returns.
I usually try to support the opposite idea by bringing agile to the table. Agile doesn't say "please don't overengineer" but "this can change a lot in a couple sprints, requirements may be different, there are more (or none anymore) use cases now" and hence why to spend so many resources doing something that not only doesn't cover all potential unknown use cases but also adds overhead when reading the code for no benefit. For some teams this has clicked very well. Appropriate agile training can help a lot.
However it doesn't always work and if the person(s) doing this have higher ups backing it up (even if unintentionally) you're fighting the wrong battle. If you can't change it, move teams or to a company where money is a bit tighter and/or where these behaviours aren't tolerated - in other words, where things needs to get done and there's no time for experimenting with things that most likely won't yield returns.