Oh my goshI thought you were joking. I had to check out Dennis Farina's biography here on IMDB. He died in 2013! Wow.

It's amazing they even show the Dennis Farina ones considering that he is dead.

I have a feeling there's two answers to this question. First, they're pushing the really bad Dennis Farina stuff, which have no mystery, no suspense, and feel like Farina's drank way too much caffeine. Secondand this is the sad partI think most people who remember Robert Stack's version would be surprised that time would take a toll on what we recall as so spooky and terrific. If the producers found people to edit out 1) all the UFO and historical stuff; 2) the lost love episodes of folk who most likely have all passed on; and 3) every case that has been solved, then there might be a year's worth of the chilling unsolved mysteries to re-watch. But I think a lot of the original series' persistent allure would die a quick death if the episodes were aired without being heavily edited. Not to mention that it's cruel to re-air episodes where the outcomes of mysterious disappearances have since become known.
But I'd switch streaming services if someone heavily edited the original series. I switched to Hulu when "Disappeared" started running that show, whose early years are VERY much like UM. Unfortunately, Hulu has the rights to only two seasons.