Neither do the Pharisees or the Sadducees or any other Jewish sect have any edifices at Qumran attributed specifically to them.
Apparently few (if any) Jewish sects of the 1st century labeled edifices they used, as none named them as edifices belonging to THEIR sect - at Qumran or anywhere else.
Does THAT fact translate to none of the texts at Qumran as possibly stored there by any members of the sects of Pharisees or Sadducees? No. The mere fact of the lack of attribution - naming a location as the location of any particular sect, does not preclude the presence of any particular sect there - including Pharisees, Sadducees - or the Essene.
"appear to have been an insignificant and short-lived ascetic sect living in a remote area, had no connection whatsoever with Qumran"
An opinion, not a fact, and one of many different opinions on the issue that cannot - either way - be proven by the few available facts. It is as subject that will probably be debated among religious scholars until the end of time.
"and their alleged authorship [by some] of the Dead Sea scrolls is a ridiculous modern fiction belied by the texts themselves"
SOME say the idea is 'ridiculous', while others say that denying the possibility is ridiculous.
It is enough in such matters to say "I believe . . . . . . . " and leave it at that.
An opinion, not a fact, and one of many different opinions on the issue that cannot -- either way -- be proven by the few available facts.The only idea that isn't supported by the few available facts is Essene authorship. It was saddled on quite soon after the discovery, and simply doesn't have any basis. Despite this, it has been repeated many times, and continues to be, and has picked up lots of true believers.