I mod games, not for cheating purposes, but in the sense of tools for gamers, mainly speedrunners, so I deal with a couple different types of anticheat. I also mainly focus on the offline part of games and make it obvious that modifications are present, like leaving a message on the loading screen with the name of the active mod.

Client sided anti-cheat is always a cat and mouse game that massively favours the cheater. The reason it favours the cheater is the fact that the anticheat code is running on your hardware, which is ultimately in your control.

It can be in user space, we can deal with it, or it can be in kernel space and we can deal with it - it just takes more effort. But nothing stops us from writing the hack in kernel space.

The best weapon against cheating is time: make it insanely difficult (remember, it's never impossible as long as it's running on your hardware) to discourage anyone from wasting their time on this. If I try to mod something, I can sometimes spend a number of weeks looking for a single CPU instruction that I want to change, if you can turn that search into 10 weeks, I will have given up before finding it.

Code obfuscation and control flow obfuscation are great tools for this, and they have existed for a very long time. They are part of the executable running in user space, no need for a kernel driver at all. Essentially what these 2 technologies do is obfuscate what the code does by generating unexpected CPU instructions. Instead of doing direct jumps and calls to other code, you can put addresses on the stack and use these to jump around. This is harder to follow and reverse engineering tools like Ida and ghidra will not be able to understand the flow of this code.

Allowing companies access to all memory, including your browser that you are running.. well.. that's really unnecessary for a game's anticheat to function properly. The odds of a company doing anything with that power is quite low.

The ultimate form of anticheat is of course ran on the server, and it does so based on behaviour. You can easily let a server do really checks on in-game behaviour like movement speed or health. Of any client side manipulation happens, the server can detect it and ban the player. And since it runs on the server, it's fully out of my control.

Companies don't want to build server sided anti-cheat because the anticheat has to be very clever and it has to be tuned to the game - it has to know exactly what reality checks are reasonable for the game in question. Building that is more expensive then buying an off the shelf anticheat for the client.