What is your proposed theory? It is understandable to be sceptical considering the scandal that was proto-altaic, however there is evidence in form of successful reconstructions of PIE languages.
This brings up the topic of standard of evidence that's considered acceptable in various fields. Successful reconstruction of PIE languages is similar to mathematical derivations in theoretical physics. In physics, successful derivation of mathematical results would not be considered "evidence". Evidence is mostly limited to observed phenomenon. Linguistics as a field seems to accept reconstructions as evidence. Which is cool. But it is interesting to consider the implications of using the standard of evidence of physics as applied to Linguistics, because it would certainly weaken (not eliminate) the case for PIE. It may create space for inquiry into non-PIE-assumed theoretical work.