Jelico wasn't a bad captain because of what he did. he's a bad captain because of how and why he did it.

remember, the whole reason that he was assigned to the Enterprise by Admiral Bitchqueen was because he convinced her that Ryker was too unprofessional to handle a mission of that severity. Which, he fucked up pretty badly. One has to wonder, though, if it might not have been better to send Cairo, instead of the enterprise while they dealt with their captain who had been taken prisoner by the Cardassians. or even better, have sent Jelico and Cairo on the covert mission while Enterprise did the diplomatic thing (which was kinda their job anyway. They're basically a mobile embassy armed up like a battleship. exploration just happened when there was nothing else to do.)

I don't think the change in starfleet's culture was all on Jelico. It's incredibly difficult to change culture like that- even on a single ship. Genuine leaders know this and, in the place of a short term command, they don't even try. They change themselves to fit and operate in that cultural framework.

While Jelico may have been technically correct on a lot of things, and people can go round and round arguing about four shift or three shift crew rotations, the reality is that he was going to be be there for a few days and Picard had things the way he wanted, and would presumably change them back. Any half-baked leader would know that it takes time to make the kind of changes he was instituting. Just for the crew shift rotations alone, that would take a month or more before the circadian rhythms of the crew weren't feeling out of whack and they were back to peak. Doing it when you know you're likely to be going into battle in the next few days is asinine.

Further, he didn't communicate with the crew. They didn't feel the urgency he felt, or the need to be "peak" because, frankly, he didn't tell them shit. he told them what to do and expected them to do it, even though his officers on the Enterprise are themselves qualified as commanding officers and highly experienced (both in combat and in tense diplomatic negotiations. Again, the Enterprise was Starfleet's diplomatic flagship.) So that lack of urgency in their prep was more Jelico's fault than the crew's fault.

he was like that all over the place. Dismissive of Troi's suggestions and advice in handling Ryker and the rest of the crew, dismissive of Ryker's advice, of everyone's advice. He didn't trust them to make decisions and was implementing bullshit changes without explanation or even a reasonable timeframe to get it done.

Which only served to alienate the crew.

The crew was expecting to go into a tense diplomatic negotiations with. The crew that he was ignoring despite this exact thing literally being their exact area of expertise within starfleet. He's an idiot and shouldn't be in charge of an automated replimat, never mind a captain (and what the fuck? they made him an admiral?!)

yeah he was technically right about the uniform, but that conversation could have gone much, much differently. ("I understand that as ship's counselor, you want to keep things casual and comfortable, but you're not just a ship's counselor. You're a vital diplomatic aide, and I need you to look the part. Not because I'm being a jackass, but because it's important we project professionalism and unity.") (seriously. he was an ass in that conversation.)