I do not agree.
Dismissing this problem as one that will fix itself is kinda naive to me.

Bitcoin nodes basically only do one thing: validate blocks. That's why anybody can run them. That's why the decentralization works. They require low processing power, low space. People don't need an incentive to run them (hell I ran one on a 13 year old PC with a Pentium and some additional HDD slapped on)

Nostr relays don't have a set limit to their applications (literally "AND OTHER STUFF"). Basically, they could be doing anything at one point. Especially with the pace at which things are developing.

Right now people run relays because they like to and they might even be relatively cheap (I don't know), but at some point it might become so burdensome that they would need a revenue model. And few people will use paid relays.

You could end up with a situation like Tor, where 2/3 of the network is in the hands of three letter agencies that don't mind doing all kinds of nasty shit.

Anyway, just my opinion. I hope I am proven wrong.