How do I get rid of pudding face in immigration? I did some tweaking and it’s still happening

If we are talking about resident household sim immigration, then the relevant settings are on General Options > Options:Lots > Options:Immigration/Emigration provided that the Immigration Gauge is set to some value higher than 0. There are three possible sources that can be used for the arriving sims' genetics.

1 - Sims in the Household Bin (default chance is 50)
2 - EA version random sim generation (default chance is 10)
3 - Resident sims already in town are used (no setting for this, it's 100 - the sum of the first two, so the default chance is 40)

It's the second option, when it gets used, that tends to generate zero-slider sims. The first and third options can also do so depending on what kinds of sims are in the Bin or already in town. If they are more varied in either case, then more varied incoming sims will be generated. So what have you got for the first two options and what other tweaking have you done?

If we are talking about the generation of homeless NPCs, then the relevant settings are on General Options > Options:Sims > Options:Immigration/Emigration provided that Replace Service Sims (and/or Roommates) With Immigrants is set to True. The SP Population add-on module is required for this one.