Only it is, that's what the previous six movies have quite clearly established.
"Over 20,000. Even Master Yoda doesn't have a midichlorian level that high."
"-No Jedi does."
Again, this only makes sense if you very forcibly ignore the six earlier movies. Which by all means is anyone's prerogative, to consider Disney's take more canon than George Lucas's. But TLJ is the outlier in this case, not the rest of Star Wars.
I'll agree with you here though.
Go watch the movies again. Rey being a Palpatine fits pretty much all of TLJ, except for when Kylo tells her, her parents were nobodies. But a) Kylo is the bad guy, who b) wants her to join her cause, so he has every reason to lie to her, and c) Palpatine could have easily hid his presence, much like Luke did. Kylo is an untrustworthy source. JJ should have just left it at that instead of bending some convoluted back story into a shape that fits both. Although I can understand with all the other petty retcons that that would have really riled people up.