Making all tackles legal would be a real bad idea. It's super easy to just severely injure an opposite player with a nasty tackle to the ankle.

Fake injuries should be discouraged by simply stopping the clock and resuming once play resumes. And fake dives for penalties can be discouraged with the VAR and giving yellow cards more easily for fake dives.

Also, I personally feel that talking back to the referee should be punishable by a yellow card. In almost no sport it is allowed in any way, yet in football it's almost the norm to start an argument with the referee once the whistle blows.