The time to criticize Democratic party is when you run, support, canvas for a better candidate, (better candidate in the framework of Democratic party, since US is a two-party system at the moment). If you’re doing nothing for a year and just start shitting on the party when it’s close to elections, you’re a willing on unwilling conservative supporter, it’s simple as that.
If you believe that you will be able to just get third party going, not only you’re braindead, you actually don’t care about lives of other people, and optics are more important than people to you, which makes you a bad person with bad morals.
If you just sit around, waiting for a good candidate to materialise before your eyes, you’re just braindead.
That’s why Dems only run establishment boring candidates and don’t want to change anything, because their support is steady and consistent.