Alternative theories to Social Fascism?

Hi, I’ve been very interested in the Comintern’s existence and it’s effect on the global Communist movement as well as how the movement had affected the Comintern.

(For TL;DR read the last paragraph, thanks)

In hindsight, it seems the supermajority of Leftists dismiss the theory of Social Fascism as too simplistic at best and actively harmful to the movement and helpful for fascism to grow at worst. After Hitler’s rise to power was consolidated, the Comintern did a 180 and advocated the theory of Popular Front, AKA ally with anyone who isn’t a fascist to take down fascism and restore bourgeois “democracy”.

Again, a large portion of leftists, though perhaps not a supermajority, also derided this policy as extremely ruinous to the movement. Its worth noting that a major mark of shame against the Comintern’s leadership at this point was its refusal to mention its theoretical mistakes during the “Third Period.”

However, if we remove hindsight and look at history from the POV of a Communist in the mid 1920s, the theory of Social Fascism and the theory of the Third Period seemed to hold definite water.

The Koumintang, thought of as Social Democrats (I guess at the time, but I pretty much consider the Post-Chiang organization Completely Fascist) slaughtered the Communists who under the orders of the Comintern tried to ally with the KMT.

And though this occurred after the declaration of Social Fascism, the bloody riots known as Blutmai in Germany seemed to also prove that the SPD were bloodthirsty and would ally with Fascism over Communism. In Germany’s case it should be mentioned the the Social Democrats have a long history, whether exaggerated or not, of bashing communist insurgents, which definitely brewed some bad blood between the SPD and KPD.

So, my question is, if Social Fascism is wrong, what, for the Communist movement, would have been the correct approach? Furthermore, as I am aware (my surface level understanding) that Stalin and Zinoviev were proponents of Social Fascism, were there other communists or Comintern members that had alternate theories?