People go where there is money to be made, no mystery there.
But to say we're in a bubble just because blockchains are successful is like saying Google Adwords is in a bubble because advertisers keep bidding higher and higher for top position for their ads.
Where there is demand, prices will increase.
I think the general consensus is that yes, coins for which there is a higher demand are rising in price and market cap. However, shitcoins that there is absolutely
no demand for are also making huge gains in price, sometimes much more significantly than the coins that actually provide value. So people think that, at some point in the near future, the altcoin market will crash, leaving only Bitcoin and a few others standing. That is at least the extreme interpretation of it.