It's probably worth pointing out, here, that most of the tropes one would expect in a "Spy TRPG" are probably cinematic in nature, with apologies to Fleming, Bond, Le Carre, et al.
Indeed, and if it's not good at any of them, doesn't give the vibes, just "technically has rules for" them (in the way literally any RPG can technically have rules for literally anything, even if it's inherently terrible at them), I have to wonder what the point is. And I guess I know what the point was - cash in on the d20 craze!
It's kind of sad for us because we were pretty hyped for both Spycraft and d20 Modern (I was super-nuclear-hyped for the latter, even!), and both were disappointing in the end, mostly for similar reasons.
Why is realistic spy stuff "obviously" outside the purview of level-based RPGs?
Because the PCs all start at low level and slowly work their way up, and they're so profoundly incompetent at low levels in most level-based RPGs (certainly all D&D-based ones, albeit 4E had the problem less than others), that it's completely implausible they'd be sent on missions (you could perhaps make it plausible by setting in wartime France and have the PCs as La Resistance or something, but that wasn't the general assumption).
You could in theory make a level-based game which worked with this, but it'd be a weird kind of level-based, I suspect, or high-starting power, narrow range of levels (like only 1-5 or maybe 1-10).
And what cinematic stuff can't it do anyway?
Any kinds of stunts or behaving like a character from movie will just get you killed at low and low-mid levels in those two d20-based games. 3.XE is fundamentally mechanically hostile to that kind of behaviour, including in 3.XE itself, because it has so many specific rules, those rules generally amount to "make the player roll multiple times, if any of the rolls fail, they're screwed" with any kind of dramatic action. Whereas games like Feng Shui actually had rules to make this stuff work, and in 1996 even.
Also, as I noted above, your PC is profoundly incompetent even at stuff they are explicitly trained in at low levels (let alone general spy skills, which they won't have all of!), so quite aside from getting killed, you just fail at stuff constantly, over and over. Low-level badguys also tend to fail at stuff a lot, so even in combat you get some really funny farcical stuff, but you don't get "spy action".
You seem to be under the deep, deep misapprehension that we didn't play these games significantly, that we weren't excited for them. We were excited, and we did play them a lot for a few months trying to get them to work ("Maybe if we just get to higher levels?" etc.). I'm not speaking theoretically (though it's been a long time, obviously, over 20 years).
You've already said you don't care for or about cinematic action, so I'm not expecting you to suddenly turn around on that, and it's fine, but it is a thing.