The thing is, most people who call their defense the best in the league do so seriously. Most people who say they suck are doing it half jokingly as a response to them being overrated.
The reality is, they do have a fairly good defensive core, but aside from Backlund, their forwards suck defensively and it makes everyone look worse as a result. Especially since their defense is built around offensive dmen.
They also don’t have 3 or 4 #1 dmen like Calgary fans usually think. They might not have 1 at this point even. They have 3 dmen in the #2-#3 range, a #4, and a #5. They also have an abundance of currently crap dmen to try on the bottom pairing with Stone.
And in regards to Smith, I’d say if anything, he’s propped them up at this point. He definitely hasn’t made them look worse.