What I have personally seen is that, although average Muslims have throughout the centuries, usually believed in the concept of blind belief in
Hadiths, this, however, has not been the attitude of notable Muslim scholars. Muslim scholars have gone critically through all the traditions and based on their differing reasoning and understandings given different conclusions. When it came to traditions that were ambiguous, either due to content or reliability, there was difference of opinion, giving us with a range of conclusions, which in most cases has been recorded in our books. For example, in the case of keeping beards, while there have been scholars who have termed it obligatory, there also have been others who have termed it as preferred but not obligatory.
For traditions whose evidence was pretty much unequivocal, there wasn't much difference of opinion and the conclusions were pretty much the same. This, I believe, is the case for
Salat.
One thing that you have to understand is that, the kind of work that was done by the early
Muhaddithin is extremely extraordinary. From what I have read,
any logical method of historical criticism that can be thought of, was used by these scholars to criticise the narrations of the Prophet that reached them. Additionally,
A'ima Rajal (scholars who studied the characters of the narrators) also provided us with an invaluable service. Javed Ahmad Ghamidi (the Pakistani scholar) in one of his talks said that he, for years studied the methods of the
Muhaddithin and did it with the objective to find some fault in their methodology, but he was unable to do so. Therefore, he, although reaches different conclusions, uses the same methods of historical criticism used by the
Muhaddithin.
For example, from a video I once saw (I think it was Sheikh Hamza) the ruling in the matter of raising hands after
Rukuh is based on
Muttawatir Hadith (or some other strong evidence) but Imam Malik and Imam Abu Hanifa did not accept it. Imam Abu Hanifa gave the reason that the person from whom the tradition was narrated, himself was not known to do it. Imam Malik gave the reasoning that, thousands of people of Madina did not use to do it.
Apparently, while average Muslims might have accepted completely the
Kitab-e-Sittah (or the Shia' Hadith books) notable Muslim scholars, even today keep on critically analysing the traditions. On the matter of "... scholars arbitrarily determine what is a command and what is a recommendation...", I really don't think that happens. Even if some group of scholars does this, there would be another group of scholars who will oppose them. Because of the presence of different Islamic schools of law, such callous handling of Islamic law does not appear to be possible.
On the matter of
Bukhari, I doubt your assertion. One thing that you have to keep in mind is that unlike today, when these books were being written, the scholars didn't just accept them without any criticism. The scholars of those times had no (at-least for the most part) conflict of interest, that they wanted to promote a particular interpretation of Islam. These famous books became so popular because they held against criticism, and were comparatively extraordinary works. Now, I am not saying that there cannot be anything wrong in them, but what I
am saying is that, huge extraordinary efforts have been made on determining the reliability of these traditions.
The Pakistani scholar's name is Javed Ahmad Ghamidi. Wikipedia article:
https://en.wikipedia.org/wiki/Javed_Ahmad_GhamidiMost (if not all) of his work is in Urdu, although some has been translated into English.
