You can evaluate officials on a range of metrics, such as anonymous surveys on corruption, air pollution, even fertility rates if you want to go for that. GDP targets are silly. Sometimes you have to do tough reforms which will lower GDP growth rates in the short-term to boost it in the long term. For example, China's bloated housing sector. By putting out elevated GDP targets you're undercutting such efforts and local officials are encouraged to forget longer-term issues in favor of short-term GDP targets.
You evidently have no idea how modern China is governed, so please stop with the pointless conjecture and distortions, what next shall we go back to harping on about the great leap forward, the cultural revolution and how everyone in China is starving and oppressed!
I mean that 40 year 'short term' boost which lifted hundreds of millions out of poverty is just silly, we need to think 'long term' let the peasants grind a couple of centuries more, because my dogma says so, or is it just more communist propaganda, those cities are just photoshopped and the numbers are fabricated!
You don't have a monopoly on silly ideas!
As a counter example, money politics, in the so called 'greatest democracy on earth', creates 'legalised' corruption so should we not bother with elections? or just ban money? Or is it OK because 'rule of law' says its fine! I mean a hereditary Monarchy would fix the corrupt election problem, right, let's do that.