It's a sad fact of Starfleet training. Perhaps the Khitomer Accords left them less concerned at preparation.When your security staff training is at "Rent A Mall Cop" level, I'm not surprised.
i think one of the biggest aspects of TMP going forward was the ask first, shoot much later policy that dominated Starfleet's politics. They prefer to emphasize the diplomatic aspects of each culture, highlighted in the Babel conference and the rather toothless response to the Romulans sending a spy amongst the Vulcan delegation. Starfleet prefers to handle things by talking, rather than emphasizing martial prowess, save for as a last resort.Exactly, there's alot of training knowledge, tactics, manuevers, tricks, fighting styles to pick up from all the history behind Androia, Vulcan, Earth, let alone any other member worlds that might join.
Luckily they showed a bit of competence with the MACO's.
Even DISCO showed a bit of competence by being properly geared up for away missions and having a tactical vest.
And, Starfleet struggles to learn the lessons from the past.