My two cents on how to achieve left unity:
Anarchists: Stop using the word tankie. It pushes your fellow leftists away and pisses them off. Instead make specific criticisms of communist countries. ESPECIALLY stop calling MLs “red fash”. There is already enough misinformation going around about fascism.
Marxist-Leninists: Embrace critical support. Be willing to criticize and accept criticism of nations like China, the Soviet Union, and especially North Korea. Remember that being against US imperialism is not the only thing that makes a country good.
This is a non-starter for me because I don't just want to "resist neoliberalism," people have been doing that for decades. What inspires me is the idea that I am actively building the socialist future, and if you are a Marxist that is done in the context of the party. I am done with big tent DSA type orgs because without a consistent ideology, you honestly can't make an organisation that will pose a threat to capital because your actions will end where your internal disagreements begin (so for anarchists and MLs, anything more than anti-fascism and anti-capitalism creates discord).