My biggest problems with Trump are his protectionist trade policy, his character, and the general stance of the republican party on criminal justice reflected in his original appointment of Jeff Sessions.
Those are criticisms I have of Trump, and given my disdain for a lot of the Democrats' platform if they don't cut the other way on the things I disagree with the Trump administration on they are going to find it nearly impossible to earn my vote since they aren't offering anything I find to be better.
Kamala Harris seems to be something of a protectionist herself rather than a free trade person, her moral character as someone with virtually the same sexual ethics as Trump and her obsessively racial lens through which she views the world isn't a winning point for me, and I don't trust her with criminal justice given her record.
Beto on the other hand is actually in favor of free trade and (at least in his Texas run) lower corporate taxes because he's not economically illiterate to how economic growth works, and he's given me no reason to doubt his character or his sincerity when it comes to criminal justice.