While both parties gerrymander, Republicans are the worst offenders. More Democratic states turned over their district drawing to neutral drawers. Republicans did not join them. Trump is leading the charge to gerrymander more often. Democrats like California’s governor are temporarily overturning their states’ neutrally drawn districts in order to combat Trump’s aggression.
Fair maps are needed to improve U.S. democracy, but even fair maps won’t be proportional because of where people live. You’d have to get rid of the district system altogether if you wanted representatives to be proportional to population.