The concentration of gains up the cap spectrum isn't itself a precursor to weakness; it's the lack of participation from the "average stock" that warrants some caution.
An ever-popular question these days is whether the October 12th, 2022, low for the S&P 500 was "the" low—and thus, if the bear market is over. The short answer is no one knows, and that may be the case for some time.
To add more color to the debate, the chart below shows the maximum percentage declines for all S&P 500 bear markets since the 1960s. If the bear market did indeed end back in October, it would have lasted for 195 trading days, which is about average when considering the entire sample size. If the bear market is still ongoing (meaning, the October low is to be broken through), this bear is getting longer in the tooth, now being more than a year old.
That length isn't unprecedented, however. Sticking with the possibility that the bear market isn't yet over puts it in the company of bears that started in 2007 and 1968 (and beyond that, 1973, 1980, and 2000). The worst-case scenario would be something akin to the bear that started in 2000, which was clearly the most frustrating drawdown (in terms of timing, not magnitude) in the collection below.