That's a commonly made statement, and I don't claim to have a basis for definitively disagreeing with that statement. But I have heard some historians claim that many of the regions of China had better governance in the 1930s (some under "warlords," and some under the KMT central government) than China has had at any time under the PRC regime. That would be an interesting historical question, and probably depends on which forms of "oppression" one counts and which subgroups of the population are most regarded in the analysis.

Even as I knew Taiwan in early 1982 when I first arrived there, when Taiwan was still a one-party Leninist dictatorship that practiced censorship and even political assassination, it was a less oppressive place than China is today, in my personal view of what is oppressive and what is not and who is most oppressed.