I think Einstein must be wrong to some degree, possibly to a large degree. Scientists for 70 years have been trying to make Einstein's theories compatible with quantum physics and failed ..... For large planatary objects Einstein appears correct, at quantum level his theories are fairly useless.
Einstein's E=mc^2 formula being correct doesn't automatically means all his other 'thought experiments' or gravity assumptions are actually right. Some think it is possible to modify Newtons laws slightly and keep E=mc^2 still true.
Nor does Einstein's prediction of effects like a 'cosmological constant' hold true. This predicts at rate at which the universe is expanding - it's simply wrong. So many theories have been adapted to make Einstein still correct, such as thoeries on black holes, etc.
Even Einstein towards the end of his life began to have doubts.
".. there is not a single concept of which I am convinced that it will stand firm. I am not sure if I was on the right track after all."
Albert Einstein age 70
Before Einstein, scientists believed in 'aether' theories, a background medium through which light travelled, I'm not saying these are true either but these type of ideas were dismissed too quickly (rather than modified to fit) alternative aether like thoeries could still exist and not contradict e=mc^2