Fun part is, they did so much it's unbelievable. They were handled severely broken justice system, a bunch of judges that were appointed by the same person they tried to persecute, a bunch mechanisms and systems were completely dismantled, the majority of supreme court are outright taking orders from a outside organisation.
In less than 3 years, they managed to gather all the insurrection perpetrators, used smaller ones as a fodder to persecute bigger ones, overcame all the corruption and bullshit, got cases such tight, they even managed to "al-capone" the biggest one, to the point that was actually convicted of 34 cases. By the standards of the American judicial system, doing so much to a conservative bunch with ties, money, and power, is probably unprecedented.
But then America decided that they would rather have that convicted felon in charge again, and all this hard work went to shit.
Do I think it's good or fair? Absolutely not. But given the system they had to operate in, Democrats in general did a good job. The obvious answer is, the system is shit and needs to be dismantled and reorganised, but that's not what Democratic party is, and it's not what it was elected to do.

I doubt they’ll go after the system as it is unless we get more progressive candidates in.

Absolutely correct.