It is a horrible process and takes way too long.
One BIG complaint I have and others who live in states that don't have Primaries until May. We in WA don't get the chance to vote for our favorite candidate, maybe even somebody we donated money to. By the time the election reaches us, states like IOWA and New Hampshire of all places have eliminated our candidate.
I think it should be a 2-stage event. 1st Stage - Separate Primaries over 4-weeks. East Coast, Mid West, Mountains, Pacific Coast - and by popular vote the top 4 candidates square off for the delegate race, which is the 2nd stage. This time the Pacific coast goes first. Election 2020 the order would be reversed.