There are < 1500 validators on Solana at the moment. That is about a single row in a datacenter. If Solana wants to continue avoiding a majority attack, that node count will have to scale. Solana is PoS which is better than PoW but still has way more power usage as it's still a blockchain than Visa.
Can you explain the environmental critique a bit?
A Solana transaction consumes about as much energy as two Google searches. Where exactly would the environmental damage come from?