Good point - also both new Admirals are pretty insubordinate and tend to disobey Sakazuki's orders. Wujitora especially does NOT tend to give a damn.
I can't see Akainu, Kizaru or Kuzan being that way to Sengoku.
Kuzan let NICO ROBIN escape Ohara back in the day and didn't kill Saul (well, it could be argued that he didn't go hard on Saul but left him to his own fate, yet he ultimately survived). Kizaru did "kill" Vegapunk recently, but he went easy against Luffy and Bonney (everything indicates that he even helped them) and the mission was ultimately a failure (even if the marines don't know about Vegapunk's survival yet). The original admirals aren't really loyalists...
Issho is IMO being set as a turncoat, but Aramaki is probably the best admiral in terms of loyalty so far (might be even better than Sakazuki, as he tends to get up their nose).
The world was bound to be in turmoil the moment this new era began, regardless of who leads the marines
Marines lost Sengoku, Aokiji, with Garp being an honorary marine, regardless the statement has nothing to do with actual powerscaling lol
”Akainu’s leadership and determination lead to a stronger version of the navy”
Basically, Akainu is more aggressive than Sengoku, he began his reign by moving MarineHQ to the New World as a direct challenge to pirates. You can also expect Akainu to be ruthless against corruption, the last thing he wants is a marine slacking off from his duties. The whole organization just runs more efficiently under a stern ambitious and ruthless leader like Akainu unlike the retiring Sengoku who was more compliant with the way things were
Yeah, the story would need a 20+ year timeskip if Jinbe's words were the absolute truth, but even then we can't see even the minimal changes made by the marines in the world (actually, Oda was the responsible to put himself in this dead-end alley)... the major change in the timeskip happened with Blackbeard taking Whitebeard's territory, that's all. Post-skip, the Supernovas (especially Luffy, Kid and Law) made the most drastic change of all, toppling down two Yonko... and the WG IMO did a bad move by abolishing the Shichibukai (Croc and Doffy were indeed harmful, but pirates like Mihawk and Boa would never do anything if unprovoked), making yet another Yonko crew. IMO, they at least could've taken down a Yonko crew or two (BM Pirates/Beasts Pirates), at least we would get rid of one awful arc (either WCI or Wano, or even both). Or maybe at least take down or capture a Supernova like Kid... if they did it, the Wano disaster would never happen, for example. Only pirates have been changing the world and the marines never do nothing to stop them.
The marines didn't lose Sengoku, he's just semi-retired now, but was seen on duty post-skip (he was in the convoy escorting Doffy to Impel Down and might've even helped to sank Jack to the bottom of the sea). Garp's the same too (well, they lost him now, but he's still alive). However, you could say that Akainu isn't on active duty anymore, because he's apparently always too busy with paperwork. (But if a Marineford 2.0 were to happen, I think that they would be stronger.)