Right now, about half of the coins in the top 50 have delivered better performance than $BTC over the past 90 days.

This is entirely reasonable when considering the market backdrop: after a strong sell-off at the beginning of the year, prices mainly trade sideways, with irregular swings up and down, rather than following a clear uptrend or downtrend.
When $BTC fails to create a strong enough trend, capital often rotates into altcoins to chase short-term profits. Therefore, the fact that many altcoins have outperformed in the recent period accurately reflects the nature of a “choppy” market—where opportunities are selective rather than broad-based.
The last time altcoins truly outperformed across the board was right before the peak in September/October. After that, when the market weakened, performance also diverged even more.
At present, the indicator measuring how much altcoins are outperforming is in a half-and-half state—not overly hot, but also not overly pessimistic. This suggests that the market is waiting for the next move from $BTC.
If $BTC breaks out clearly in one direction, altcoins are very likely to react more strongly in the same direction. If $BTC continues to move sideways, the divergence and capital rotation among altcoins may persist.
In short: altcoins are “waiting for orders” from $BTC. And in a phase like this, picking the right coin matters more than trying to guess the market direction.