I have twice typed up huge novels and deleted them.

The very, very simple answer to your question is that I do not think the Democratic Party is liberal. They are a centrist party that pretends to encompass the left because U.S. election law is set up in such a way that only two parties can prevail at a national level.
The why? Those are the novels I keep writing - Election law/electoral finance laws and money. The parties won’t fix the laws, and money skews right. Thus, even the ‘left’ party is in the center.

I say I’m liberal because that’s where I fit with the understanding I have. I did stipulate a U.S. liberal, because - the ‘spectrum’ has always been understood by me to be roughly defined left to right as revolutionaries, liberals, centrists, conservatives, and reactionaries.
Reduced even further, it’s just left, center, right. Liberal, centrist, conservative.
Because I view liberals as separate from centrists, and the Democratic Party as centrist, I don’t view them as encompassing my beliefs. (And, there are a number of actions they’ve taken or not taken that run contrary to my beliefs, too.)

I think that I overlap with leftists on about 90% of views, honestly, but I’ve been attacked and told I support genocide in leftist communities when literally the only thing someone knows about me is that I don’t want republicans to gain power. I’m probably sort of sensitive to the assumption that liberals are supportive of every action of the Democratic Party. My ‘liberals that want revolution’ was a bit of an intentional reversion to the overly broad grouping. Not intended to be an insult - more or less a dumb joke best accompanied by a shit-eating grin.