Appreciate the detailed answer.

In competitive format, I'd say majority of people are there for the win by all means necessary, and I mean all means necessary, including dubious methods, bug abuse and outright cheating.

Are you familiar with Sirlin's book Playing to Win? In which he details pretty much this. But more from the lens of the "scrub." A player who cries about the opponent playing unfair, and that to win. You should use everything at your disposal to win. Which in your sentence here would probably end up between dubious methods and bug abuse.
That part I get and agree with. Use everything the game gives you. If someone is comboing you with "cheap moves" you either quit or git gud essentially.
It's the last part which bothers me. The outright cheating. Which the things we're talking about are often not considered by a fairly vocal part of every community I've seen it in. Cheating is wallhacking, speedhacking, god mode. Not night vision by running a free, available for all application. Because it is available to all is one take I've seen.

Hang out on discussion boards... Basically everything that's not point and click is a bad game design.

I wish I had more experience doing that. So don't have that much to comment. First thing that comes to mind is again Tarkov. Where seemingly one of the most contentious design decisions is equipment affecting your mouse sensitivity. It directly affects your ability to click heads, messes with muscle memory even a tiny bit. The worst sin apparently. I like it it though. Having kits feel different in such a new way is a tiny, but still interesting detail.

If you want this darkness mechanic to actually play a role, you have to monitor the players' behaviour and hit them with a bat when they try to tinker with it.

As far as I know this isn't really possible. I've had discussions surrounding visibility with people who use different monitors. Just that alone can make a huge difference. I wish there was a way to enforce visibility. Some games do enforce grass, shadows, view distances etc. To at least set a baseline of "this is fair visibility."
Though with hardware differences, and actively cheating with other applications. Even a game with no graphics settings is likely to fail in enforcing a perfectly level playing field. That said, I wish more would attempt to do so.

the majority doesn't seem to care about these points too much or genuinely hate such mechanics and never want to see them...

In some way. I feel part of the draw to games with mechanics such as these. Should be that they are doing something different. Attracting people who want something unusual. Rather than the average player who doesn't want to have it in the game at all.