True. Most of his theories are just formulas on paper, not reality. For example, you can add negative integer numbers on paper, but they don't exist in reality. For example -5 + -3 = -8. But negative integers don't exist in reality, only on paper. So if you have a formula full of stuff that doesn't even exist in reality, it's useless and pointless.
Also, the fact that relativity was invented to explain why the Michelson Morley experiment of 1887 failed to detect any motion of the Earth, so that science would not have to admit that the Earth is stationary and admit that it was wrong, makes the theory suspect. It didn't come out of a search for truth, but as an attempt to repair a broken paradigm that was refuted, which was that the Earth moves.
However, some say that relativity is proven in a number of ways. For example, supersonic jets carrying atomic clocks have been shown to slow down time the faster they go for days on end. And the GPS satellite system supposedly cannot work without relativity in the equation. A lot of guys on YouTube have mentioned this. It's technical and hard to explain, but that's the gist of it.