No, oil gelling appeared before the MTBE -> Ethanol switch. It appears to be caused by hot spots in the engine combined with the much thinner oils used today to meet EPA regulations.
I've often thought that we ought to run a compettitive test between 1) an modern automobile engine, tuned to run on regular without designer fuel and newfangangled additives, without emmission controls and artificial design restrictions on breathing ability and 2) a similar engine with all the current EPA and car companies best efforts to obtain high mileang and low emmissions.
It would be interesting to see just how far off the mark a well tuned old technology approach is to todays standards and at what cost. My bet is that we have spent hundreds of billions to achieve very little that couldn't have been done by mandatory tuneups and elimination of older oilburning junkers.
I once owned an BMW M6 with a "worked over" engine - and it passed emission tests with just a minor leaning of the fuel-air mixture....and it hated ethanol laced fuel - mileage went down markedly!!