how do electromeric / inductive effect theories compare with resonance Back in high school, long time and many seas away, I learned about electrons moving within organic molecules based on electromeric and inductive effect. Googling them today, I found that they are deemed obsolete by IUPAC, but still used, mainly in Russia and India.

True, today, for my limited chemistry needs, I can make do with resonance. But how did +E, -E +I and -I become obsolete? Is a mere statement of the various resonance structures enough to fully convey the information stated by describing those effects, or were they rejected for some inaccuracy?

Also, were these effects part of Chelintsev's "Marxist chemistry"? That would explain their historical and geographical extent.
The concepts of electromeric and inductive effects are not obsolete.

Only the term "electromeric" is obsolete and has been subsumed in the terms "mesomeric effect" (+M and -M) and "resonance effect" (see iupac source). The term "isomeric effect" is still in use and I learned it not a decade ago along with "mesomeric" and "resonance".

Amusingly, your SE question is my first result in google for "Marxist chemistry". From the little I have just read in this book, Marxist chemistry had apparently more to do with refusal of the concept of resonance than anything else. So... maybe? Maybe not.