I know that there is a great myth built around the Corvette Navy in Canada. And no doubt the very miserable existence and resulting hardship suffered by that "branch" of the navy means that it developed a narrative of its view of the war that made it worth it to fight in that way. However, and this is the sad historical truth: The Corvette Navy achieved very little other than rescuing merchant seamen from their sinking ships and fooling those same merchant seamen into believing the navy cared and was protecting them.
The corvettes were an emergency program begun shortly before the beginning of the war as a stop gap measure to produce a lot of cheap little vessel very quickly, with minimum equipment and basically useless of the task other than showing up, to stop the gap until the real anti-submarine vessels (the much larger castle class corvette/frigate and the river class frigates, together with some C and V class destroyers) arrived and air power could be brought to bear every where. The basic corvettes* around the convoys achieved a less than 2% efficiency in stopping submarines in the first three years of the war. In that time, however, 90% of the merchant ship traffic went through unscathed as a result of routing of convoys. By the mid 1943, the larger ASW ships arrived in strength, together with the escort carriers and the tide was finally turned. Our Canadian "Corvette navy" myth makes little out of the fact that, while we acquired and operated 111 corvettes in WWII (only 14 of which were acquired after 1943), we also acquired and operated, starting in 1942, 55 Castle class and river class frigates, 7 destroyers (not including the tribals, which were all serving with the RN nor the old american four-stackers, that were little better than the corvettes) for convoy escort duties. These were ultimately the backbone and most efficient vessels.
My point here is that we should stop looking at a wartime emergency measure as the model for building the Navy in peacetime, when we have all the time needed to get the actual ship you need for the task you conclude is yours(If Great Britain had the time in 1938, they would have gone straight to frigates and destroyers without bothering with corvettes). If we build now, with the time in hand, we should build the proper ship for the job we do.
And, BTW, I am happy to see that Chris dragged the Holland class patrol vessels of the Dutch navy in the picture. The Dutch have four o those ships, but guess what, Chris: A single Halifax takes all four of them out without even a scratch on her paint. That is how useless at war fighting they are. Ah! You ask: Why do the Dutch have them then? Just like many European continental countries (and the UK), the Dutch use these vessels for constabulary work of their government, law enforcement and overseas territory "protection", which means drug/human trafficking and police work (in the case of the UK, they are used for fisheries protection only).
That is fine for those countries where the government has adopted that legal framework and scheme for its action at sea. In Canada, we have not. The legal framework in which we work assigns war fighting only to the RCN. The law enforcement rests with the RCMP, fisheries protection with that part o the Coast-guard, etc. etc. So we, in the Navy, do not have the legal authority to act as a constabulary force++. This may change but it is a government decision.
I agree with Lumber just above: The government has to decide first what mission it wishes the navy to have, then pick the proper ship for it. But so far our mission has fallen between the number 2 and number 3 suggested by Lumber, and that means that the lowest vessel that can effectively do the job is a frigate - and when we have time in hand, that is what we should build.
*: By the time the larger, more effective ASW escort ship started to arrive in numerical strength by the end of 1942, the corvettes could finally start to be taken into long refits and finally fitted with all the ultra modern ASW equipment that had been developed for the frigates, so that by the end of the war, the corvettes that remained bore no resemblance with the ones that had fought the first half of the war at sea.
++: That is, BTW, one of the never resolved problem with the AOPS. The government which ordered those vessels, and the current one, have yet to adopt legislation that empower the Navy to act with the AOPS. It is domestic peace time ops we are talking about here and the rules are not the rules of war - thus not operations under Rules of Engagement. For constabulary work, we need proper authority (peace officer power under law) and proper use of minimum force rules and training. It has not yet been approved, or even developed. Think about it, a merchant ship is doing something fishy in our waters and an AOPS sees it. On what basis can the Captain act or use his gun? Without legal cover, she wouldn't do anything but report to the RCMP.