The main explanation I heard about Falling Rock was construction on the street made it impossible to get there but I don't think that is true given all the other bars on the same block having no issue staying afloat.
IMO Falling Rock fell off because they didn't want to cater to the popular hazy/pastry/kettle sour trinity but they also didn't try to drive interest in what they wanted to sell. By the end their taplist looked more like a chain craft beer bar's selection than one of the leading craft bars in the country.
Falling Rock was the first place I tried a lot of classic Belgian beers years ago. Thirsty Monk brewery was good too but they closed last summer I think. Cheeky Monk was a good belgian beer bar but they've been closed a long time at this point. Just doesn't seem like much interest in Belgian beer anymore.
Bruz has a couple locations including one not far from the old Thirsty Monk location. De Steeg tucked away on Tennyson is also all Belgian. Both breweries suffer from not making their beers as crisp and digestible as Belgian versions but that seems generally true of most American takes. We're definitely in a lull for the abbey/trappist styles but saisons aren't too hard to find around town.