Nice excluded middle there. 
Who’s making up anything, suddenly or otherwise? There exists a certain skillset, which hasn’t changed in a century or more, that is necessary in order to be a good judge (cites available upon request). Why is it “a new set of criteria” to say that senators needn’t confirm someone who doesn’t outwardly possess that skillset, unless or until the nominee can convince them to the contrary?
Well, my point–and if you can find anything contradicting this, it’d be of interest to me for my paper–is that stealth nominations, or the deliberate selection of “nominees without legal writings or whatever,” is a recent development. (There are a slew of reasons why this might be so, beginning with Reagan’s realization in the early 80s that lower court nominations were just as important as Supreme Court nominations when attempting to further a particular judicial philosophy, and encompassing the decline of patronage, the failed Bork nomination, and several other things.) Thomas, Souter, and now Estrada. It’s a great strategy, if and when it works, but it’s probably not within the spirit of the advice and consent clause (not to mention that it probably isn’t particularly efficacious, something I address in my paper). But it’s not a question of the Senate having been reluctant or unreluctant in the past, because present-day nomination strategy is different than it traditionally has been. This is intrinsically neither good or bad, but it’s true. Therefore, your assertion that confirmation norms should remain static is curious to me.
And none of it reaches the question of Estrada making a good judge. This thread was started because someone, off-handedly, called Estrada a judicial candidate “perfectly suited [to the federal court],” whose nomination was undeservedly blocked by partisan Democrats. Later posters have amplified that theme, though none of them have stayed in the thread long enough to defend their position. I’m not attributing their arguments to you, so I don’t know if you believe Estrada was undeservedly blocked or not. But I don’t see what the reasoning of the Democrats in blocking the nomination has to do with why many conservatives assume that Estrada is “perfectly suited” for a D.C. Circuit appellate court seat, this latter question, essentially, being the thrust of the OP.
I find it puzzling that you seem to be advocating that senators confirm judicial nominees about whom they know nothing other than a resume bereft of judicial experience, a nonresponsive confirmation hearing, and the good word of the opposition party.