The Tang royal family was Xianbei, who were Mongols, as was much of the nobility in the northern dynasties of the northern and southern dynasties.
Anyhow, my point still stands that the Qing wasn't desperate, nor was it doomed to failure. It was a perfectly normal Empire by the standards of the time.
I don't understand your logic. If the Tang as you say, were actually "Mongols" (I've actually never heard that theory, but please, don't bother finding literature for it, we're not going to hem and haw over that point), doesn't it disprove your point?
The Tang objectively did better than the Qing in most respects, as outlined in my last response, or at least rivaled it significantly in your opinion. Doesn't that like...show that "a non-Han dynasty" that really really "Hannified" could last and do so much longer than the Qing? It just showed that it wasn't a "standard" non-Han empire by standards in any dimension, it was sub-par.
I'm saying that the Qing policy and their attitude from the beginning was doomed for failure.