I don't care for Karma-farming, but I liked having some way to tell if someone was a real community member or a throw-away account. I liked that there were some subreddits that wouldn't let you post if you had low karma because it helped hold back the trolls.
You can spread powder on the floor so you could see if someone had stepped in. It wouldn't keep them out unless they didn't want anyone to know they'd been in there.
"Here is how platforms die: first, they are good to their users; then they abuse their users to make things better for their business customers; finally, they abuse those business customers to claw back all the value for themselves. Then, they die." Reddit is in step 4.
You're completely right from a user's perspective. I think this post from Cory Doctorow helps explain what we're seeing. He doesn't talk about Reddit specifically, but it should be easy to infer the implications for Reddit from what he writes: https://pluralistic.net/2023/01/21/potemkin-ai/