First, your assertion is wrong.
Secondly, even if it wasn't, it's still flawed reasoning. Those same cup winners didn't need John Tavares to win those cups. Does that mean that he's not worthy of a first round selection?
It's absolutely insane to think that those goalies aren't worth 1st round picks. Dude, the odds of a player even making the NHL in the late first isn't all that great. Why they hell wouldn't you take a chance on a highly touted goalie? Makes absolutely zero sense to not take them.
It actually makes all the sense in the world. Here is the order at which players tend to be able to come in the NHL the fastest : Winger-Center-Dmen-Goalie. Goalies take by far the longest to develop. That means you get less bang for your buck on the pick. Kopitar has provided so much more bang for their bucks to the LA kings it's not even funny. For example, Price's first real good season as a starter for us was 2010-11, whereas Kopitar had already posted 285 pts in 318 reg season games by that time. And while Price was good in 2010-11 (5th in vezina votes), I'd say he was still not as valuable as a 6'3 ppg center at that point. The year after that price did nothing of note and was as interchangeable a piece as they come. So 7 years after the draft, Price had given us 1 top 5 vezina season, a solid rookie season, and a lot of growing pains aside from that while Kopitar was a full blown consistent ppg two way #1 center who could do it all.
And Price is an example of a goalie being picked in the first round who is a success.... If you look at goalies picked top 10 over the past 20 years, the miss rate is quite high. The odds are really against you big time when you select a goalie in a draft as opposed to a forward or even a dman. And that is because, as shown above, goalies are so far removed from their top potential that they're much harder to properly scout. It's just a bigger risk and crapshoot....
Then that's compounded by the fact that since 2005, players become UFAs much sooner. If your #1 pick has not given you a lot of quality years already by the time he's 25-27.... you're risking losing him to UFA. At the very least you lose your leverage and you're forced to overpay before you have actually seen him be a consistent performer for you.
Then you must consider the opportunity cost. There are more and more quality players available for each position. Consider the fact there are only 64 spots for goalies in the NHL. The quality at the position is increasing all the time, and it's not like teams can hoard goalies. You can only have 2 realistically (3 technically, but it's an untenable situation). It's well known that value of commodities are dictated by offer and demand. For goalies, the demand is low (64 spots as opposed to skaters 384 spots), and the offer is getting higher all the time with the talent pool of goalies getting deeper with less demarcation between the top and the bottom. That means goalies are low value assets in general compared to centers, wingers and dmen. Getting an elite #1 center is actually really freakin' hard... and even then, even if you get an O'reilly or Tavares... there's still a gap between getting that and a Malkin, Crosby, McDavid, Draisaitl, etc. Same thing but to a lesser degree with wingers. And you've said it yourself countless times, we need to tank to get those guys. The few times where we have a top 5 pick... we should really take that opportunity to draft the guys that you can't get otherwise. Because for example, we would have been way better off spending cap space on say a Halak + Lehner combo than having Price + some no name back up who can't hack it. It would have taken approximately the same cap space, and would provide more value because we would get 82 games of solid goaltending as opposed to 50-60 games. Not only that but then your goalies are in better shape for the playoffs, and you have a safety net in case of injuries.
And look, you may try to tell us with all the assurance in the world that it makes no sense not to draft a goalie in the frst round but the reality is that NHL teams have avoided drafting goalies in the first round in general over the past 15 years for exactly the reasons I mentionned above. I even heard Alain Chainey say on TV that many teams' GMs actually forbad drafting goalies with first round picks.
Drafting Price in the first round top 5 overall was akin to using your life savings on lottery tickets, coming out ahead by 100K and calling it an amazing decision. It was a stupid call, that turned out well... but where the odds of all of that happening weren't great.
But yeah, it's actually pretty dumb to draft a goalie with a first round pick in today's NHL.