First Pass The Post is democratic, but the worst way of it. In most districts, 40-49% of voters are disenfranchised by gerrymandering.
Mixed Member Proportional is far more representative. If you assume certain minority groups vote as a bloc, then you can't gerrymander them away like our current system does. The proportion of people not getting representation is capped by 1/number_of_reps.
The whole "republicans in Senate stop the government from doing anything" needs to end. Parliamentary systems means the legislative body and head of state agree to work together. Our system means deadlock most of the time.
Finally, "senior members" of the parties in both houses are the only ones who decide what bills can be voted on. That's not democratic. Every member should be able to bring at least some bills up for an up-or-down vote. Make them vote down "healthcare for veterans" instead of killing it in committee or amending it to add "only if you strip women of bodily autonomy".