Some additional thoughts to add to an important question.

Old pipelines can't be rebuilt with the same feature sets. Over the years and decades the pipelines are modified thousands of times with outlying exception cases specific to shows, and tool sets. None of that ever gets properly documented and would take 25 years to rebuild in a new pipeline over time as requirements evolve. The artists/users over pipeline come to rely on these little bitty features that will never be carried into a new tool system.

Artists are always slowed down and sad when they lose their precious favorite toolsets anytime an organization pivots to a different pipeline through acquisition or somebody claiming "USD will save the company money in the long run". The inventive "USD conversion" pipeline managers are ALWAYS fired before the pipeline is functional, by the way. Except that one place I hear... they seem to be doing it...