Actually, people can use lag switches, and that's very easy to use. But I'm not sure it helps to make yourself lagging in order to kill others. Apart from that, any network-related cheat seems hardly doable. This is in no way comparable to the degree of "undoability" of an autoblock cheat.
However, as someone who had one digit stable pings on the pecores server for a very long time, I really notice the difference with 30-ish ping, which I would objectively consider very good. I hate 30-ish ping compared to lower because even though all your actions are near-instant, the game sorts of prioritize players by latency (either explicitly or naturally, it doesn't really matter). Maneuvering around enemies (getting in their back, being able to "push" and not being pushed yourself...) are very different when you have higher ping than them. And "very different" means that "high" pingers (that is, higher than the opponent) will be pushed away, have their movements roll-back a little, be confronted with enemies that seem to be impassable concrete walls, and be unable to "block" the enemy's movements in the same way (soap effect).