There's a quite promising (and successful) method for judging policies and organisations when up-to-date inside information is wanting:
Look at patterns and typical preferences.
This is much less inaccurate than to extrapolate the past.
I do apply this very often, and also presented some standard models that describe patterns. Niskanen's budget-optimising bureaucrat and the principal-agent model apply to seemingly all bureaucracies at least to some degree.
Another pattern I mentioned (many years ago) was that technology advances from one arena to another as it becomes more compact, more lightweight and/or simply less expensive.
Some areas of military affairs are kept secret for decades, not mere years - and become visible to outsiders (which includes the vast majority of actively serving armed forces personnel) only when applied on a grand scale in a conflict. It's thus extremely difficult to form an informed opinion on military affairs as a whole.
This is a problem in a democracy, for it requires a break between principal (the sovereign = the people) and agent (the armed services) somewhere. Somewhere along the chain of political decisionmaking there's a leap from ignorant to informed. The voter doesn't know military secrets (that were kept secret for real), and thus has to authorise policies (including spending) without being fully able to decide on basis of actual information instead of propaganda.
This issue can be reduced greatly by applying a substitute for accurate information; the interpretation of what's non-secret with the knowledge about patterns and preferences.
Everytime an air force general who was a fighter pilot argues for new fighters you take it with a grain of salt.
Everytime an admiral complains that no warship was christened for a year and asks for more shipbuilding funds you take it with a grain of salt.
Everytime an army general argues for some fancy HQ or new tank battalions you take it with a grain of salt.
Their recommendations may be good ones, but it's utterly inappropriate to trust them entirely. If in doubt, one should conclude that they could do the job with less than they ask for - at least if they did a better job than they do.
On the other hand, it's rather not likely that the demonstrative confidence of the armed services in old key equipment is appropriate. A stealth fighter concept won't be utterly dominant in a high end conflict against a capable opposing great power that had the motivation, the means and 30 years time to devise countermeasures. Anti-ship missiles developed in the 1970's and upgraded only within the limits of their original concept are not going to be anywhere near as good as actually new ones of the same class. Anti-tank munitions (which in the West have a proven history of lagging behind the best Soviet armour designs) of more than 20 years age are not reliable against high end opposing forces MBTs, period.
This may sound "sceptical", but keep in mind that the other path is called "naive".