A 55" TV is still the perfect size for many situations. In the U.S., it is second only to 65" TVs in popularity. One of the great things about 55-inch size TVs is you can get a lot for your money.
There is no one "best" TV for all purposes. Some 55" TVs are designed for outdoor use, others do their best work in a darkened room, and others look like artwork hanging on a wall when not acting as a TV. The trick is figuring out which one works best for your needs: If your room is bright, check out the mini LED and QLEDs, if the space is usually darker then OLED could be the ticket.