People who want to learn, already have the means to learn. Increasing the availability of learning material wont suddenly magically compel players, which do not care to educate themselves, to seek out knowledge.
You need to force players to learn and distinguish themselves from less invested player with game design decisions. You grow and improve passively with time, repetition is key to learning any skill and a one time tutorial wont fix that.
The problem is that mobas are competitive in nature and the overarching endgoal for every player should be to be the best player or the best player they can be. This obviously conflicts with Blizzards intent to make it widely available and as easy to get into as possible.
Blizzard needs to keep both sides at the opposite sides of the player spectrum happy, which is very difficult. From all the years in hots and having observed and played all the changes they introduced or tried to introduce, it is clear that they dont have an idea how to achieve that, which is not surprising. The biggest problem is that their attempts at changing something (or changing something back) feels like an eternity.
If you would ask me what they should try to improve...
They already even have a system they could use to attempt and imprint certain skillsets and behaviours onto people without even touching gameplay design.
And its called daily quests. Even Hearthstones quest system is more complex than the one from Hots. No one is gonna learn how to play support from "Play 3 games as support" and then even allowing them to queue as whatever they want in unranked.
Rework the incentives for the daily quests, give the ability to reroll quests once per day instead of completion in unranked, hl and tl, make them require actual work and investment and add a ton of hero specific or generic behaviour quests.
For example:
Daily Quest:
"Tyrande follow up stun": Land a lunar flare on an enemy within 0.5 seconds that has been displaced or stunned by a teammate.
Progression: 0/50
Reward: 1500 Gold or 1 epic Lootchest
Daily Quest:
"Support slow cleanse": Remove a slowing effect from an allied hero in combat and under 50% health.
Progression: 0/25
Reward: 1000 Gold or 1 rare Lootchest
Daily Quest:
"Mercenary timing": Capture a mercenary camp during the countdown timer of an upcoming objective.
Progression: 0/12
Reward: 500 Gold or 1 common Lootchest