Opening summary is needlessly long and I simply skipped it to get to the analysis. I think a better, short summary would be to quickly describe the archetype, environment, and/or role of the monster in question, then move on to the in-depth lore section later (which you do).
I feel like your analysis of the stat block also doesn’t match with mine. You consistently reiterate that the aboleth is a tough or frightening boss and it isn’t. It’s honestly one of the weaker legendary creatures and has counterintuitive design to boot. If you’re interested I can give a rundown of its stat block for now I think that’s unnecessary.
Some of your lore assumptions seem really off. I personally estimate a 0% of an aboleth charming a kraken. The kraken has a +11 wis save and the aboleth must be within 30 ft. to attempt the enslaving. If it doesn’t win initiative or fails to enslave, then it is dead, period. The Kraken literally cannot miss the aboleth outside of rolling a 1, and since aboleths are smaller in this edition (they are large) it is immediately consumed, which is fight over, since the aboleth doesn’t have enough damage to escape its stomach.
Similar story to a lesser degree with the dragon turtle. It has a +7 save against enslavement, which isn’t as dominating but is still formidable, and once again thrashes the aboleth in combat. Worse, if the dragon turtle is aware of the aboleth’s presence, it can use lightning breath before the aboleth can close in, worsening the scenario still.
Aside from the fact that this is highly unlikely to occur for mechanical reasons, making it happen outside those reasons is simply bad design. A kraken/dragon turtle will obviously smear any party even remotely close to the aboleth’s CR, and higher level parties will vaporize the aboleth if it even gives them 1 turn of knowing where it is, essentially making it an absent force in its own lair. Seriously, it has 135 hp. Look up how much damage a party can put out in later levels, it stands no chance.
Additionally, while your ideas of aboleths controlling towns and pirate fleets and such may have been correct in previous editions, it certainly isn’t in this one. Any agent the aboleth wants to keep reliably controlled has to fall into two categories: it has to be within 1 mile of the aboleth consistently, and it must not take damage reliably. Examples you give like pirates would not be under an aboleth’s control for long, since the distance alone would give them ample opportunities for the relatively easy DC 14 will save.
Even if all the above is handwaved, however, I still found your lore section to really just reiterate what has already been printed about aboleths in the current MM and before. There’s really nothing innovative or creative that might invigorate veteran DMs, and new ones will see more or less what they’ve already read in the MM.
That said, I do hope you keep it up, and I’ll check out future videos of yours to see if I find them more agreeable.