Well first no, the democrats position on trans rights for example is more left than lots of places just look at the UK. Even some position on healthcare don’t universally line up as centrist. But more importantly shouldn’t we define these terms by the political situation on the ground? The dems are at very least on the left wing of American politics
Don't forget that what is considered centrist has shifted over time. Hell even giving fair and equal civil rights to all peoples was a radical leftist idea not too long ago. Before the civil rights act passed the country was very much in favor of a lot of the "far left" ideas being proposed today.
Totally, my point is less about what's right. Honestly the trans stuff is a big reason I can't see myself living in the UK right now, but about where the parties exist in the range of public opinion and the US democratic party is a left of center party by most definitions I can come up with
