Imo, the biggest problem right now is ETH. It was $8 at the beginning of the year. It's so severely inflated, that if it keeps crashing, it's going to keep taking everything else with it. That's what happens when you let a competitor gain too much market share. It's stupid that I find in order for BTC to hold its price, or continue rising, that requires ETH to hold a 13x inflated price (since the beginning of March).
I agree with you that ETH is severely overinflated, esp when I have the belief that it was never even intended to be a cryptocurrency in the first place (Vitalik himself said that) and thus hold any significant value. It's been pre-mined to death, and the float is tiny. But even worse, the ETH fans don't even realize that the mining floor is somewhere down around the single digit dollar area, and troll traders took millions of ETH off exchanges for pennies for the last 2 years in anticipation of running it up to the moon. Notice that I said troll traders, not people who actually believe in ETH and are long term holders. So any weakness in buying demand, or any flaw/bug found, or any exchange hacked, and ETH will get dumped into the absolute ground.
But I disagree that this will affect BTC to the negative or in any way whatsoever. It's completely disconnected. If anything, they'll be trading back into BTC on the way down.
Perhaps not only disconnected but negatively correlated. ETH (and XRP) falling means BTC dominance in percent going up, and some investors think along the lines of "if Btc ever loses its top position then all trust in crypto is lost". A price correction of some over-inflated altcoins makes the market look more sane and less bubbly.