Nostr clients need banscores for misbehaving relays, and relays should be ranked based on performance, with clients prioritizing higher-ranked relays. There could even be incentives for optimally performing relays. For long-term sustainability, incentives need to be in place for optimal relay operators, as experience has shown that "nobody works for free." I suspect a significant issue with Nostr's performance is due to people running cheap relays on subpar VPS.