It's a fact that the Blue Jays think it's easier to scout amateur pitching. I don't think it's about a lack of development. They just draft a lot of arms.
On one hand, it's not a good approach because of the failure and attrition rate of pitching. High school pitching is the riskiest of the four main draft prospect types.
But on the other hand, pitching makes for very fluid trade currency because every team in baseball always will covet controllable pitching, to some extent. Whereas if you have a hitting prospect at a specific position, you might simply not line up with teams that have depth at that position.
Also, if the organization truly is better at scouting pitchers then that could overcome the attrition "risk" of amateur arms and make selecting them more often a viable strategy.
Further, you need to invest in pitching somewhere. Maybe it's a more sensible prospecting strategy to load up on arms, and try to create a pipeline. Even if many of them fail, as they will, you should have more cheap ones coming. And then when it comes to the major league payroll you can invest heavily in hitting there, in the place where the injury risk of pitchers really hurts when you get dinged by it.
This is ostensibly what the Blue Jays do, from the outside looking in. They spend most of their amateur budget (~$10M) per year on a truck of amateur pitching, let it develop over time, and spend most of their major league payroll in any given year on hitters. Vlad Guerrero jr. might have been a slight deviation from the normal plan, but they still had 4 of their top 5 rule 4 draft players as pitchers.