Naxos

The 2019 season is just ending and hotel owners are taking a break from 18 hour days for the past 6 months. Many hotels are not yet focused on the 2020 season yet so its not surprising that you are not getting a response.
Ippokampos is an older hotel that has been fully renovated. Its directly across the road from the beach. The ground floor rooms are actually half basement and anyone can see into these rooms so not very private. The whole area around this hotel is bars and tavernas. It may not be quiet at night.

We stayed at Kymata in September. Second and third floor rooms facing the water have 180 degree sea views. Third floor views are totally unobstructed. Second floor room still had a pretty good view. Kymata is in a much more quiet area.

Check the booking.com website for available hotels in April and check the reviews and photos they provide. You can focus your search on St. George beach by first finding a hotel for St. George beach then using the "show on map" function and clicking on the "balloons" for the other hotels there.

If you can get one of the only two top floor rooms at the Kymata , SNAG THEM , the views will take your breath away every single time you see them ! Huge deck , and close to beach port and town !
I’ve stayed in the standard rooms too , they are fine , but the top floor rooms are the best , the views and that deck seal it for me

There are quite a number of hotels with sea views in St. George area ... sometimes not on street level but on upper floors. One that I haven't stayed in but have recommended to 2 people who liked their rooms and their balcony views AND the hospitaly very much, is Hotel Palatia (not a palace despite the name! but a friendly family-run place with 3 floors). Another fine one, near the far end of the beach is Villa Naxia (not listed in online agencies; contact direct), very attractive & serene, just a few yards back from sands, lovely rooms & service. The 2 hotels right ON the sands with ALL rooms have balconies facing the sea -- Studios Kalergis and Hotel Asteria... both very well located. Studios Diogenis (close to both of these) has a lovely cafe out front where I had breakfast several times this June (but not a late-night place w. noise). Don't know if it would be open in April. You have many choices. Good tip from stanbr about Ippokampus; i'd often wondered about it, but forgot about the club scene.

I agree with Brotherlee on a good way to scope out best locations ... use booking.com, go to "map view" for your dates, and see exactly where the "balloons" are vis-a-vis the beachfront.