Our current front office/scouting staff have been in place since 2011, maybe 2010. Not sure how to really distribute credit for the 2010 draft, so let's just say 2011 onward. Point being, I don't see drafts from 15-20 years ago as relevant at all to current team draft philosophy. The game league wide, as well as our individual team's management/scouting team, has changed drastically since the late 90's and early 2000's. Hell, even our owners have changed.
Even looking back as far as 20 years, I doubt the Blues are alone in rarely drafting players below 5'10", especially in the first round. I would be curious to see how many teams have drafted a player shorter than 5'10" in the first round between the years 2000-2010. Wouldn't shock me if more than half the teams in the league did not. Drafting shorter players is becoming more common, and this year may change the veracity of the following statement, but I believe there STILL has never been a defenseman shorter than 5'10" taken in the top 10 of the NHL draft.
Am I still misunderstanding your point? Because in the IMO more relevant time frame (roughly since 2011 under the current management team), the Blues drafting players 6'0" and under is more common than them drafting players over 6'0" in the first two rounds. Even if the Blues drafting a player shorter than 5'10" is even rarer (A.K.A. nonexistent lol), I still think you're overstating the significance of a trend of drafting for size. Would the Blues have to use a 1st on a player 5'9" or shorter in order for the trend to be reversed in your eyes?
As far as DeBrincat goes, 29 other teams passed on him in the first round, and 7 other teams passed on him twice that year. Granted many of them may feel silly now, but it's not like the Blues were alone there. If you're trying to say that a player being short should not be an automatic disqualifier for using a 1st round pick, I agree with you 100%. But I don't see a notable recent trend of the Blues coveting tall players or shunning short players in recent early round picks.