This here shows what is creating this disagreement; a major misunderstanding of advanced stats and how they work.
Metrics like RAPM CA (isolated impact on shots against) use predictor variables to compare a player's actual results to a baseline results based on the context surrounding them. For every second of a shift where you don't allow a shot, you are out-performing the baseline expectation. For example, if you start a 60 second shift against Boston's top line in the defensive zone, and you're playing with average teammates, and you don't allow a shot against, you will have out-performed the baseline for CA and your RAPM CA for that shift will be a negative number.
These metrics actually do give plenty of credit to guys like Vlasic and Doughty and what they did when they were on. In fact, these metrics give so much more credit to Vlasic in particular than anybody else did throughout his prime, which is why it's so weird to me every time I read something like this about Vlasic. (It's not the first time I've read it either - I've seen Sharks fans use this same argument in defense of Vlasic posting atrocious metrics over the past two years.)
From 2007-2008 through 2017-2018 (when Vlasic and Doughty were both actually good), not only did Vlasic have the highest net RAPM xG+/- impact of any defenseman in the NHL, but the gap between he and 2nd place Chara was larger than the gap between 2nd place Chara and 10th place Dan Boyle. Right above Boyle is 9th place Drew Doughty, who definitely was very highly regarded by these metrics as well.
If you'll notice, the "xGA" column contains your proof of a negative right there. Vlasic's xGA impact of -30.58 shows the Sharks allowed 30.58 fewer expected goals with Vlasic on the ice than they would have with an average player; his defensive value alone is enough to get him into the top-9 on the net impact chart.
Speaking of proving a negative; Doughty's impact on shots against was literally
the best of any defenseman over this sample, and his net impact on shots was only 2nd to Erik Karlsson.
And while defensemen can't consistently influence goal-based metrics, Doughty ranked 2nd in net goal impacts, and Vlasic ranked 7th over this same sample.
These metrics give plenty of credit to what players like Doughty and Vlasic did in their primes. In fact, I'm sure that now that I've posted this, people are going to tell me these metrics are useless because they rate Vlasic so highly.
Karlsson actually falls far behind both of them in expected goal impacts and goal impacts, which is why if you haven't noticed, I haven't said anything about these players at the career level; I'm not even entirely convinced that Karlsson has had the better career than Doughty, and I can see an argument for either player. I definitely think that Karlsson was the more talented, and dynamic player, but as a whole, his impact on quality shot and goal shares was pretty underwhelming relative to that level of rare dynamic talent, where as Doughty had a pretty strong impact.
However, what I am taking issue with, is these completely unsubstantiated claims that Karlsson has been
bad over the past 2-3 years, or that Doughty has been better. All of the evidence shows that Karlsson has been far and away the superior player, and the gap between their results over the past 2-3 seasons is past the margin of error of interpretation of these stats; if you want to look at these stats and say that Karlsson's results haven't been better, then you have to be discrediting these stats entirely at that point. (Doughty was better in 2017-2018 but has been clearly inferior in the two most recent seasons and has been clearly inferior if you aggregate these 3 seasons.)