That is true, but then so were most countries a few hundred years back. No-one is pretending that Tibet was some kind of shangri-la before the invasion. It wasn't. Life there was always quite tough for the ordinary people. But, when you compare that with what they have suffered under the occupation, it is clear that they are now infinitely worse off.
The Chinese invaded for two reasons, to asset-strip Tibet of its resources, and to impose the new-found and manic-obsessive Marxist ideologies of Mao Zedong upon them. Ideologies which led to so-called the Great Leap Forward, and millions of consequential deaths by famine in China. Somehow, feudal society seems positively benign compared to the murderously insane regime of the former Chairman, a regime which is now considered an embarrassing part of Chinese history which even the Politburo would rather not talk about.
China has modernised to some extent since Mao's day, however the present government is reluctant to let go of Tibet because of its mineral wealth, and because it serves as an overflow-zone for their overpopulation problem.
IIRC, the present Dalai Lama has in any case stated that he does not intend to return to a feudal style of government should Tibet regain its independence, but would look to a more modern infrastructure.