You know that how? Because if game follows some baselines from HoI2, you can completly ignore espionage or diplomacy and still be perfectly fine.
Problem with your apporach is that you assume that R&D, Diplomacy and Espionage will have equal importance in game, which most likely not happen. To be exact, it shouldn't happen, as in wargame diplomacy is secondary issue, espionage might or might not work, while R&D will be your bread and butter in winning wars.
That's why game requires balancing systems here to ensure, that out of 4 sliders it will actually make sense to use more then 2 - and that putting 100% of your spending in just one field will result in potentially disastrous effects. Ability to switch your whole nation intellectual resources from developing nuclear bombs to becoming the officers on the whim or sending all of them to spying your enemies is both unrealistic and highly exploitable.
letting go of espionage is not an option IMO, because it consists of spy defence too. What use has more tech slots when your opponents have for example %75 chance each time delaying your research?
people at paradox are working to make a balanced game and I trust them, this is how I know that. At the worst case they can put min levels to certain sliders (perhaps tied to your ideology) so that you cannot put them all to zero.
I think you can try to be more positive and constructive. I am trying not to sound like a fanboi because I am not but the dev diaries impress me. I have a lot in my mind that I expect and most will probably not be in the game but a great game is always a good game and I trust Paradox will make a great game. For example I would be more happy with a tech system where you open projects and companies make bids and you select some of them for prototypes, after the prototypes are ready select one for production and so on but it will not happen. I can choose to be negative and curse everything else but I try to be positive and I get impressed by the work done.
Sorry for the ranting, it is nothing totally directed to you, I just am fed up with everybody cursing every single thing that they did not want.
Back on topic, 21 tech teams will get meaningless after some point where all relevant techs for the historical dates are researched. There will be 21 teams making close to none progress in their overly-rushed topics while enemy spies are roaming freely in your land forces command HQ full of IQ<50 officers while you have no hope of getting even your uncle in your alliance and trading 5 rare metals for 2 energy. In HoI2, when playing with a major, most of the time (when I am not tech-rushing something stupid stubbornly) I am already researching techs 1 year further than the actual date.