Bouchard's defensive skillset is not very good. He Skates slow, moves the puck slow, isn't physical at all, plays with zero aggression or intensity, has bad positioning a lot of the time. For the most part this gets exposed in more intense times in a game when the other team is coming hard. I would never play Bouchard in the last 2 or 3 minutes of a game with a 1 goal lead. Basically every element in a skillset a defenseman can possess to be good defensively, he does not do well. His advanced stats are good because he plays with Ekholm and gets lots of 5 on 5 ice time with the best player in the world that domnates most shifts. It has nothing to do with Bouchard's skill at playing defense. He makes lots of careless errors.
The thing with Bouchard is you have to balance the good with the bad. He is elite offensively and typically does much more good then bad, last season he was great for the type of player he is. This season though, for the minutes he plays he isn't doing enough offensively to make up for his lack of defensive ability. For the amount of minutes he plays he needs to do more offensively or he becomes a liability. I like Bouchard and get just as excited as any other Oilers fan when he rifles a shot into the net but even with his offensive totals he isn't a Cale Makar or a Quinn Hughes, those guys have way more responsibilities for their teams on both sides of the puck then Bouchard. Bouchard is still a valuable player and a weapon when used correctly and playing his best. I expect his play to improve as the season goes on. Last night was a really awful defensive effort by him though. I would have benched him after Toronto's tying goal. No excuse to make such a careless, dumb pass in your own zone late in a game with a one goal lead.