My old org managed to turn this trend around. Elected fresh leadership, new policy platform to get people excited. We took the lead in organizing a few local protests and were really picking up new members for a while.
Then the whole thing got dismantled by an undercover FBI agent who had been on the leadership committee since before I even joined. Quantico must have decided that these commies were getting too ambitious and decided shut us down before it became more difficult to do so. And that was basically the end of that.
So I guess my advice is purge anyone you think might be a cop first before you reform your org. I honestly probably wouldn't join another org that doesn't vet full members for infiltrators. The FBI threat is very much still real in the United States.