Ethereum Classic fell victim to multiple 51% attacks in 2020. The hacker was able to gain control of 51% of the hash power and reorg some blocks and it allowed double spending and all the catastrophes that come with a 51% attack [1][2].

It is safe to say that it won't come anywhere near close to where normal Ethereum is in terms of mainstream adoption.

[1] https://www.coindesk.com/markets/2020/08/29/ethereum-classic...

[2] https://coingeek.com/over-1m-double-spent-in-latest-ethereum...