Prior to the 2020s Messi reached a WC final and 3 Copa finals with Argentina so it's not down to bad coaching per se if you are always the runner-ups, Argentina simply lacked the ability to be decisive in the final. The 2014 final is a great example of Argentina being unclutch, Higuain, Di Maria, Messi, Palacios(?) missed several great chances and the final went to extra time, culminating with Götze scoring. There was definitely a mental element because pressure from Argentina fans increased the longer he didn't win anything, they even started doubting his loyalties which led Messi to briefly quit the NT. Fortunately his body held up in his 30s and a new generation unaffected by previous disappointments emerged e.g. McAllister, Enzo, Dibu, Lautaro, Julian Alvarez.
You are actually saying what I've said, timing in life it's everything, if some of those chances were scored, things could change.
Just as a side note, to be more precise: Pekerman and Basile are great coaches, that fvcked decisive moments and in the case of Pekerman, had a a very unlucky injury with Abbondancieri, even if his changes were pretty bad in my view and he repeteaed past mistakes made in prior friendlies.
Yet Sampaoli, Batista, Bauza, Maradona, too much improvisation that ended badly. Martino just a mere good coach with a serious flaw all his carreer of how to face a final.
Back to that Argentina 2014 it's actually one of the best coched NTs in recent times. The WC version wasn't the same as the one in the eliminatories that was flying at all cilinders with everyone fit (months a year after the WC, they were most of them back in their best fitness and also were playing quite great, shyte happens. but in the WC Messi was struggling on the verge of a major injury, so he was treated in consequence, Kun got broke, Di Maria too and Sabella who was a fine coach, transformed the team in way more pragmatic team to try to win it anyway, he was close, but no cigar.
PD: Yes indeed there was a mental element with huge roots even before messi arrived. That kind of stuff can only get out of the way with a Title, even if won without your best form, that it's a classic with every NT in the history of the game, if not the prior failures appear as ghosts in the new opportunities