It is, factually, a heavy capital ship as of the current day, at he price point of a much cheaper vessel due to our economising on unnecessary bells and whistles. It masses 400, 000 tons, larger than any ship to date, it mounts a heavy armament, and has resilience and shielding commensurate with its size. There is no reason to expect it to be much less able to take and receive lumps than anything we might produce at the present day. Will it be quite as good as a fancy-schmancy explorer we design with newer shields or top-of-the-line systems in a decade? Of course not, but that does not matter, because we can build two or more of these for the price of one of those, and quantity has a quality all of its own.
It does not effect military infrastructure negatively. It uses a fair chunk of it across the production run of the ship, during which time we are not doing anything else with that capacity unless we are in a war, in which case it is explicitly stated it won't make much difference, because we'd probably swap over to predominantly Selachii class escorts anyway. This has been confirmed explicitly with the QM.
