Last time I checked an unethused vote for Biden (eg Me) and an enthused vote for Biden (eg Warren Moon) count the same...
Enthusiasm is a terrible metric to go by, it says nothing about whether or not somebody plans on voting. There's connotation happiness or excitement with the word, which seems irrelevant to the current circumstance. Trump increases our collective anxiety and getting rid of him is a relief. Biden has routinely polled the best against Trump nationally and in battleground states, that's why he's done do well in these primaries and turned out new voters.
Biden is winning with prospective voters who dislike both him and Trump, which is a demo that Clinton lost in 2016. I think that's important. Moreover, simply asking people "if they intend to vote and for whom?" would yield useful data.