I would defer to the parliamentary budget officer's analysis of the force structure of the Canadian Forces and the dollar cost of maintaining that over time. That study had a variety of caveats in it, which means it's indicative rather than precise. Dave Perry has done similar work. It's about the Canadian Forces as a whole, though, and not about any one part of it.
I think fundamentally the answer is this. As less than 1% of GDP is being spent on a force that was purchased during a time when defence money was much higher, we shouldn't be surprised about the decline over time. How could we be surprised about an imbalance going forward given that the budget was effectively set in 1996? That's the low point, 1996-97, the point at which the international environment was the quietest it's been for our entire lives. It was set then. How could that budget be sufficient to provide the desired outcomes of several governments given the change in the international circumstances? For instance, neither China nor Russia were on the long-term radar for most folks despite the fact that they were then already building the capabilities they would be using a decade later. There's also the fact that Canada is gaining a new ocean. It's hard to imagine that a budget set in 1996 would be sufficient.
Don't get me wrong. I know that the budget has changed with inflation over time. But it's still pretty clear why the parliamentary budget officer and folks like Dave Perry are talking about the figures they're talking about.