It's because of the free relays. It's always going to happen as long as Nostr sites use free relays.

It should cost 1 Satoshi or less to like, dislike, comment, upload a video eetc.

This is a flaw of Nostr. That the devs want to keep everything free. Free things will just bring bots and scammers.

Basic things should cost sats. DMs for example. It should cost a couple of Satoshi to send DMs.

Nostr has a spam problem and it is going to get much worse as billions start using it.