I agree that training and good tactics, “software”, usually have more influence on winning a fight than “hardware”, modified or not. So can luck, or the incompetence of an adversary, neither of which should be counted on as part of a winning strategy.
Like I said, I don't think that incremental improvements have very much or any impact on the outcome, and given that most modifications have a corresponding drawback, aren't worth pursuing. If a fraction of a second really matters, then I've committed a grievous error elsewhere.
To give you an example of something that I think is worthwhile, I swapped out the baseplates on my Glocks with Vickers Tactical replacements. The OEM baseplates don't provide much of a grip in the event of a double-feed, while the Vickers units are nicely flared while retaining the same internal dimensions as the OEM. Very little chance of lowered reliability, but they correct a legitimate problem. I'd suggest extended baseplates are a good idea on many different designs (if you don't have a bumper on your 1911 mags, you must have a fetish for getting blood blisters on your palm), even though the chance of a double-feed is slight, and the chance that you'll have time to correct it is even slighter. So really, I wouldn't call someone stupid for not using them.
Sights are another area I think are entirely valid, although personally, I have excellent vision and they don't seem to make a big difference to me so long as I have real sights and not a J-frame-style milled channel or a pocket .380's "pyramid"-type.
But overwhelmingly, people focus on flashy stuff like triggers and barrel/slide work. I don't necessarily think they're buying a ticket to jail, nor are they ruining a handgun, I just think they'd be better off giving the money to a Bullseye master to teach them how how to really pull a trigger.