Why were the 2018 US midterm elections not an overwhelming victory for the Dems?

I expected the Democrats to take the House. Their failure to achieve a massive overthrow of the Republicans is to my mind the result of the party’s failure to appeal to its traditional base. The story in the Senate is more about the shifting demographics in the country as populations continue to concentrate in prosperous blue places, you have the increasing phenomenon of empty states with the same 2 votes as California or New York. It’s interesting to watch as all of these places fiercely shouting about the primacy of state’s rights grow ever more dependent on federal largesse for their survival.

Quite a few left leaning centrists and right leaning centrists have been islanded politically because the behavior of the right and the left right now is completely unacceptable. Participation is just low at the moment. Last election there was not one single candidate I felt really good about voting for. Midterms as well.

Too many Republicans in too many places across the country.

Well Kansas got a democratic governor and things are changing.

The Dems took 40 house seats.
That was huge! They would have gotten many more, but for gerrymandering.

Because much like over here, as an opposition party the Demotwats are thoroughly incompetent.

Frankly, I think they are so angry and inspired to act out, they aren’t mobilizing voters as much as they should be.
People tend to tune out when a message is prolonged and repeated negativity, which I think could be a significant detriment to the next election.
There’s a reason they say to put your political advertising out only a few weeks before the election, top of mind awareness as well as political burn out.