It's not that they are "silly" or "unbelievable", it's that they came out of nowhere. You think that maybe, MAYBE they might have been mentioned in the original movies. Seems something of that power would be important.
Which original movies? If you mean Episodes IV-VI, then with most force-users dead, they wouldn't factor in...
And in Episodes I-III, most force users are officially sanctioned Jedi and they don't show Jedi force-user imprisonment/suppression techniques.
That said, the Star Wars movies were mostly action-oriented...details like the ones that came out via the books (like Ysalamiri) could only have had time to come out in either a long story arc TV series, or if by chance they needed to be in one of the movies for a specific plot.
Speaking of TV series, I would love to have one set in the SW universe. Sort of like Deep Space 9 meets BSG. If set between Order 66 and ROTJ, they could avoid Jedi saturation in the stories, too.
Also, in the killed EU books, long after ROTJ there was a group of smugglers who had picked up ownership of a Star Destroyer, and it kind of served as a mobile smuggler's base. Except that the smugglers who own it have a sort of good standing with the New Republic. Something inspired by that would be a great setting for a TV series IMO. (and I saw a forum once that suggested that Martin Sheen and Pierce Brosnan could be Booster Terrik and Talon Karrde, the two main guys in charge of it)