I'll make two points.
1. Playing in front of bad goaltending is hard, if you've ever played in front of a bad goalie you'll know what I'm talking about. You run around trying to prevent what should be easy saves, you can't keep that up, you'll falter, get worn out, and give up more high quality chances again in your desperation to prevent any type of chance. Playing in front of a bad goalie makes you look worse than you are defensively, and not just because you give up more goals.
2. Bad goaltending doesn't completely take the blame off the defense, we have been consistently at the bottom for HDSV% for a number of years, with multiple goalies. I've said this many times, while our defensive metric are good there's no way to truly quantify just how high quality, the HD chances you give up are, and we give up too many HIGH-high danger scoring chances, we need to cut down on the rush chances against in particular.
That is actually interesting to explore.
In Keefe's first year: Campbell had a .844 HDSV% at ES in 6 games. Andersen had a .812.
In the Covid year: Andersen had a .803. Campbell had an .825.
This year: Andersen has an .844. Campbell has a .797 (.707 in 2022, .855 otherwise).
The top guy is usually in the .870 range for perspective.
It is a little bit tough to gauge because Keefe really has only had Andersen and Campbell (and briefly guys like Hutch, Mrazek, Sparks, etc.) as goalies. Sparks actually had a .833 HDSV%. Hutch had some good numbers and some bad. Andersen never really looked right in his last two years (whether that was just due to confidence or injury or whatever it may have been) which is evident by a lot more than just his HDSV% and didn't really affect Campbell.
Our HDSV%, at least before this collapse in 2022, was borderline top 10 in the time since Keefe has taken over (including Andersen's subpar numbers) and only marginally worse than Carolina's has been in the same timeframe. Slightly better than the Babcock teams, which were pushed by one really elite year by Andersen when he first got here and found themselves in the middle of the pack on average.
And then in CAR, Mrazek had up and down years as well. There were some years when Carolina was thrashed in HDSV%. Others where they were near the top of the league. Mrazek was actually the one consistent factor (i.e. he had a .820 when everyone else on his team was sub .800, and was always better than everyone else on his teams).
I think right now, the Leafs are a team that, if the goalie plays as well as the team in front of him, is somewhere in that .825 HDSV% range. Right in the middle of the league or slightly above there and not really that far away from the non-elite teams that are in the top 3-5. Room for improvement, but not a .720 HDSV% as we have been getting in 2022. If we want to really get places, however, we will need something similar to the .855 that Campbell was giving us earlier in the year. That is better than the defense has played, but at the same time, no goalie who has a .855+ HDSV% is there because they are just playing as well as the defense in front of them. The Leafs don't need much more than average goaltending right now because we are scoring in bunches, but in the playoffs, every goalie needs to play better than their average and the defense in front of them if you want to win (unless the goalie on the other end completely sucks).