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).
your id says it all you dont need to be degrading other coins BTC has no real use case cuz its slow and lightning network cant be fully functional.. Ethereum will have many things to their side chains and would appreciate the hodlers.. unlike bitcoin which mainly would only appreciate if you hodl.. you need to look at the coins 2 sides .. The Grass is Always Greener on the Other Side Meaning when someone is not satisfied with their own lot in life and always assumes that there are better things in other places.
Regarding the price predictions, I'm a simple man!
I see BTC dominance @70%, I sell all my BTC for altcoins.
I see BTC dominance @50%, I redistribute my portfolio so as to hold BTC again.
but i prefer not to take risk and keep my alt portfolio static i guess this EOY will bring lot of new changes to crypto market and make it more stabalize.. the worse time is actually the best time to buy.. HODL is the key