Democracy is when no political party dominates, and the more power doesn’t consolidate around a very justifiably popular party the more democratic it is.
If the democrats started doing good things the last time they had concrete control over all three branches and jumped to something like 80 percent popularity and got 80 percent of the vote, that would be undemocratic. Just like how the CPC has an above 90 percent approval rate according to international observers and holds almost all political offices in China.