When the indexes are hitting new all-time highs, it's common to see the bears make contrarian arguments. The logic is that when everyone is wildly bullish, they have already put their capital to work and there isn't much buying power left to drive stocks higher. The logic is easy to understand, but actually measuring the amount of buying power left is problematic.
We aren't hearing many of these contrarian arguments right now, because sentiment is surprisingly sedate for a market that has been trending higher for so long and is now hitting new highs. There is very little of the euphoria that tends to occur when the market move has been lopsided for long. Conditions are very different now, but if you traded back in 1999-2000, then you know what really is euphoria.
So, why isn't this market more euphoric? Part of it may be because central bankers are working so hard to keep the cost of capital low. There is still plenty of untapped buying power and the Fed is doing a good job of creating more as it cuts rates.
Unlike back in 2000, there isn't any major industrial change that is taking place like the internet. Some industries are emerging, like cannabis and electric cars. but they aren't generating new valuation metrics like we saw in the early days of the internet.
Another factor that is likely impacting market sentiment is that the ranks of retail investors continue to shrink. This market is dominated by computer algorithms and they don't get euphoric or depressed. They simply execute their trade strategy and don't worry much about the hot stock discussed at the weekend barbecue.
If you are using a contrarian strategy to this market, there is a better argument for being bullish than bearish. This is a market that is climbing a wall of worry, rather than celebrating a dovish Fed and new highs. The worry is fear of missing out and that is what keeps the market moving higher.