Honestly, an animation director's most important job is to keep the characters' arts on model, and the animation in an episode is basicliy based on the key animators who work for the episode.
So, why should we be worried for the following episodes just because that we have Takagi and Deguchi? #616, the legendary episode, was an Takagi episode. The animation in #737 was also very good but it's a Deguchi episode.
Then will we get enough good key animators in Takagi and Deguchi's episodes? Honestly I don't know, because there's a summer special and specials always take many good directors and animators away.
For example, we would have an Isouchi episode in July according to the route for directors, but we don't have it because that Guts (the company that Isouchi belongs to) is working on the SP.
But why do they have to produce specials? It's because that Fuji TV is stupid. Just like what @conan_e said days ago:
Toei is a part of the ownership tho. but yeah, it can be the other owners (FujiTV and Shuisha) who push for it.
Specials used to have really high rating, and if somebody watch the live streaming of special, he/she will be annoyed by the amount of commercial breaks and the most company is profited from this is FujiTV+ the Ad agency. and specials are not that big projects like movies (no huge variety of special merch, no special events, etc), so the revenue outside the rating are probably low, so it's likely that fujiTV is the one who request specials to be done.
