As you'd expect, I disagree completely albeit one can argue at length as to what "predominate" means. Does it apply to launcher systems or projectiles?
You are focussed on the means of delivery rather than the projectile itself. True it takes more manufacturing effort to create a modern SP than a HIMARS launcher or container launcher (for example) but once the gun is in service, the ammunition can be created quickly and in mass. You are also undervaluing the all-weather capability of gun fired projectiles and their virtual invulnerability to air defence.
The only trick, if I can call it that, is to have enough guns online at the beginning of hostilities to handle the job and that a manufacturing capability exists to expand holdings and replace losses at a required rate. True- this takes planning which the CAF does not excel at, but so does stocking other munitions.
Long story short - you need a mix of systems. I'll go this far. I don't think that the Canadian army has really gotten its head around weapon systems at this point. The fact that the artillery is thinking in terms of three 18-gun regiments, a single HIMARS regiment and relegating a few UAV/loitering resources to the tactical groups, shows me that it isn't preparing for medium range missile and loitering munitions systems at scale. hand-held drones with the infantry is one thing. Medium to long range to support a divisional close and deep fight are quite another. I'm hoping that at some point there will be a "come to Jesus" moment where the lightbulb comes on. I just don't see it happening yet.