I think Ethereum has no chance to outperform its ATH in relation to bitcoin, there is too many delays and too many competitors for ETH to repeat its peak.
Money floated away f.e. to BNB, EOS etc..
What happened in 2017 due to extremely FOMO might not happen again. At least before Bitcoin reaches its new all time high. Even when Bitcoin hits its new all time high, I agree that it is hard for Ethereum and other top altcoins to come closer to their all time highs in BTC pairs (don't mention about probability to surpass their all time highs in BTC pairs).