Absolutely, of course you can disagree with the theologians, but Stubborn stubbornly disregards almost all that they say.
Right, you can't just wave them off because "19th and 20th century theologians". On MOST subjects, they're probably highly reliable ... even if they were contaminated on other subjects, particularly EENS and leaning toward religious indifferentism. Religious indifferentism had to be condemned all the way back in time of Pope Pius IX, which means it was become fairly widespread by his day. But on most other subjects, they're generally very reliable.
There are some other issues I disagree with some of them about, such as about the notion that Univeresal Acceptance can convalidate an illegitimate election. In fact, I disagree with Universal Acceptance in general, because it would render
cuм Ex Apostolatus moot, and so
cuм ex strongly suggests that Pope Paul IV didn't beleive in UA. There's SOME place for it, but I don't think it's properly articulated. So, for instance, if Father Cekada's Aunt Helen had woke up one morning and decided that Pius XII wasn't the true pope, would she have had the right to become an SV? NOBODY doubted Pius XII. At the same time, if one believes that a Pope can BECOME a heretic as a private person (which is permitted), SOMEBODY has to be the first to call it out (despite there otherwise being UA). But then the awareness would progress from an individual doubt to more widespread doubt to ultimately universal rejection of the heretic pope. It would be a process. But according to UA, the first person to doubt it would be a heretic. I think there's something wrong with how that theory is understood.
But, apart from that, I think that 90% of work of pre-V2 theologians is reliable. Now, there are MANY issues on which there are different groups of theologians disagree, from Thomists vs. Molinists, or we had the "5 Opinions" about the heretical pope, etc. Those are fair game until the Church condemnes them.