It seems like some retconning, with the writers deciding that empathic characters are more interesting for storytelling than fully telepathic characters. It can be hard to create drama when someone on screen automatically knows what everyone else knows.

The Betazoids also didn’t have black irises, which has previously been a distinguishing feature - albeit a feature that most viewers don’t seem to notice. Given the many, many franchise references included in the first two episodes it looks like the showrunners are aware of established details, and that both the lack of telepathy and eye color are deliberate choices.

Edit: I read a suggestion here that maybe they do have dark contacts, except for Tarima, the president’s daughter. Maybe the actor didn’t want to wear contacts all day every day?

My impression was the president being deaf didn’t have anything to do with the plot, but was probably about showing that deaf people are people who have stories too. The Betazoids delegates signing and speaking to each other might be something Troi has said previously: that it’s rude to communicate telepathically among non-telepaths. But Lwaxana does it anyway because she doesn’t care. Or it might have been to avoid confusion: “they’re empathic with other species, but telepathic with each other? What is going on?” I don’t know what is the significance of taking off the translation device.

Maybe the daughter is too sensitive to telepathy?

She had that inhibitor on because if she goes out of control, bad things happen.

Or something.

I did wonder about that, but it’s entirely possible Lwaxana was on the more powerful end of a whole spectrum of levels of telepathy that exist on Betazed. Add on to that an 800 year gap during which things might have progressed in any number of ways, and I think it makes sense to accept Academy’s portrayal on its own terms and wait and see if we get more backstory/explanation as we go.

Based on what @ValueSubtracted mentioned, maybe the signing is something to do with when you’re Tan Elbrum-level powerful, telepathic communication isn’t a good idea?

Also, I felt like they did demonstrate some telepathic, not merely empathic, ability in the episode; I’ve only watched it once, so I can’t quite recall my evidence, but it seemed they could get surface-level thoughts beyond emotion, like “you’ve lost someone” instead of just “grief”. I wonder if it’s a consent/pushing too hard thing, somewhat like soothing and rioting in Mistborn; if the average Betazoid tries to get beyond the surface level of thought, the target will be able to tell, and their privacy will feel invaded.