Every time Ive been, the main pool area has been crowded. Not wall to wall, but all loungers have been taken except maybe one here and one there. Definately not 2 together unless you are there prior to 11am. Tables/chairs with umbrella go first. You really need to be out there prior to 9am to get one of those.
Captain Cook is crowded 8am until dinner time. They are open 24/7, so around dinner and through the night it is not crowded.
Lobby area downstairs seems quite crowded from about 10am through 10pm. 10:00am guests start arriving early and if there room is not ready, families often sit on the sofas waiting around, with their luggage! Upstairs the strollers start lining up at Ohana for breakfast..the lounge area if quite full until 10:30am. Lunch time, most are at Captain Cooks or the pool, Starting at 4, people start coming in from the parks going to Trader Sams, Tambu Lounge and Ohana wait area for dinner. Guests also start flowing in for the Spirit of Aloha show. The show is twice nightly 5 days a week (could be 6..but I know there is at least one night off..I think Monday??) so the guests for the late show visit the lobby, shops, look around the pool, beach while waiting to go down to Luau Cove. After the early show gets out, most walk around the property too.
Ive never seen more than a handful of people at the beach. People talk about watching the fireworksfrom the beach all the time on Dis...but when it actually comes time during the trip, they are either too tired of forget about it because by the way people talk on these threads, you would think hundreds of people are on the beach. Its far from the case.
Since the GF alligator incident, they have removed a great deal of seating on the beach and I think more people are cautious of getting close to the lagoon. Although I only saw a handful of people before, during my last trip I saw none (I stayed at YC, but went to the SoA)
In 2015 I stayed there over Labor Day. It was the final straw for me. I LOVE the rooms, LOVE the theme, but the constant people and strollers in all the common areas felt like I was still in the parks. The LONG waits for the monorail and leaving the MK on the resort monorail was horrible...very unconvenient. No peace or relaxing there. During that trip, we took the monorail over to CR to get an ice cream, as Captain Cooks was packed. It was at that moment I realized there are better choices than the Poly. It was so peaceful at the Contemporary during the day, the pool as all but abandoned. Just a few shoppers in each of the stores and no wait at Contempo. My next trip I stayed at YC. It was quiet. Didnt have to worry about broken or delayed monorails. Everything was perfect. Location to Epcot, strolling on the Boardwalk, renting surrey bikes, ferry to hollywood studios, lovely room, great restaurants at YC and BC. THE POOL !! But....I felt so far away from the Disney that I have known for years in the MK area. I had serious FOMO. No late night runs to Main St bakery, all the bustle of other guests, no dining at GF/CR/Poly. It was too quiet at YC !!! Maybe someday Ill find my happy medium!