Okay, here goes!
1) The aft elevator doesn't go down to the dining room. We both have knee issues, as well as one of our two traveling companions, so, we all had to schlep to the front elevators to go down, and, then schlep half way across the ship to the dining room.
2) Then, when in the dining room, to go to the facilities, you have to schlep cross country to get to them, passing the casino and shops on one side and the Explorer Lounge and shops on the other side. You don't have to be a genius to recognize that the facilities should be closer to the restaurant.
3) The lighting in the Observation lounge is awful. Less than half the seats are agreeable to reading.
4) The Observation Lounge does not have a coffee facility. You need to schlep from below, the coffee lounge or go cross country to the other side of the pool. Further, why doesn't the neighboring card room which offers soda and water also offer coffee. Oceania's two ships, Marina and Riviera, offer coffee, etc. in that lounge.
5) They offer two ''SLIMLINE'' elevators in the front of the ship. FDR and others should have recognized from Riviera and Marina, ages ago, that it was an awful design. Passengers in the front need to exit to allow those in the back to exit.
6) The dining room is nothing special. We prefer the openness of Marina and Riviera. We'd equate Explorer with the Viking ships.
7) The pool grill is pitiful. First visit was about 10 minutes for a hamburger. Second visit was over twenty minutes. When I confronted a head waiter, his response was'' I guess everybody was looking for a hamburger today''. I responded that he should probably still we waiting tables.
8) The most pitiful internet service ever received on a crossing. There were none even close to that bad, and, we had done over forty crossings before, including 6 on Sea Dream, a tiny ship with less than 100 passengers.
I could add a few complaints as to the service, but, I'll let that pass.