The Frozen M&G is low capacity, so I wouldn't necessarily call it popular. If it could squeeze 2,000-2,500/hr, I doubt the wait-time would be more than 20 min.
It's probably not even in the top 10 in terms of guest output. POTC, HM, IASW, Mermaid, all of the mountains, Buzz, Jungle Cruise, Philharmagic, Laugh Floor and the PeopleMover all have more visitors than the Anna/Elsa M&G on a daily basis. More people probably see the fireworks or MSEP than the M&G. I might even say Pooh. I can't imagine a M&G having more than 500-600/hr in terms of capacity. Hence the 3 hr lines.
Dumbo still isn't exactly high-capacity. Probably less than 1,500/hr. They'd need 4-5 Dumbos in order for it to be a true people-eater.
Well with CoP, Stitch, Laugh Floor, HoP, Philharmagic, Tiki Room and Country Bears, they really function as people-eaters. Which is why there's almost never a wait for any of them. 15-20 min is 'peak' for any of these.
The only thing that will ease the wait-times for the big 8 (JC, POTC, Big Thunder, Splash, HM, SDMT, Peter Pan, Space Mt.) is new, immersive adventures.
If New Fantasyland had a phase 2 (slated to open in 2016) that included:
- B&TB trackless dark ride
- Mickey and Friends circus show (Barnstormer replacement)
- Philharmagic and Barnstormer relocation to Animation Courtyard at DHS
- Peter Pan expansion/revamp using the old Philharmagic building
- IASW refurb/upgrade
- Wonderland mini-land (includes M&G and the Curious Labyrinth)
- Bald Mountain (E-ticket thrill ride, located in the very back corner of Fantasyland)
SDMT would go down to 45-50 min waits during peak times. Peter Pan would have room for more elaborate show scenes, bigger RVs, more RVs at a time, and therefore shorter wait-times during peak times (25-35 min as opposed to 60-90 min). IASW would go back to 10-15 min waits during peak times, while Mermaid and Pooh would be near walk-ons all day.
The same logic applies to other sections. If Tomorrowland were to add 3-4 compelling attractions using some of the old Speedway plot and some space behind it and Space, the lines for Space Mountain will decrease a little. Especially if the TRON speedbike coaster and an original E-ticket of sorts were added back there. Stitch could get a show between Space and CoP.
Buzz could have eased up wait times (20-25 min as opposed to 50-60 min) if Laugh Floor and Stitch were rethemed/revamped into more compelling additions.
Splash and Big Thunder might have reasonable wait-times if backstage areas were reworked to allow Frontierland expansion beyond the berm and a new pathway that leads back to Liberty Square or even the Tangled area. Western River Expedition and the old Geyser Mountain concept would do wonders for this section.
A major Adventureland expansion (with Arabia and Mysterious Island sub-lands) would especially ease wait-times for Jungle Cruise. An Aladdin show, and clones of Sinbad and JttCotE from DisneySea would cut Jungle Cruise/POTC wait-times in half since this section of the park would have more than just 2 attractions.
MK has plenty of opportunities to make up lost capacity if TDO were willing to invest in seriously reworking backstage infrastructure. Rather than spending $2-2.5 billion on MM+, they should have spent $1 billion reworking MK's backstage areas and another $1.5 billion fixing up either Epcot or DHS. Then, all 4 parks are set up for future expansion/success. MK needs 4-5 more E-tickets (DL has 11... soon to be 12, while MK only has 7). Bald Mountain, JttCotE, Western River Expedition, an original Tomorrowland E-ticket, and a B&TB trackless dark ride along with a massively upgraded Peter Pan would do wonders for wait-times and capacity. Add in some smaller experiences and better utilization of current 'dead zones' (Stitch/Laugh Floor, CoP, northern part of Storybook Circus, parts of Liberty Square, etc) - MK is in good shape.
MK needs to grow capacity to allow their older E-tickets to have leg room for refurbs/upgrades. But in order to expand MK, Epcot needs compelling attractions and some more pavillions/countries to utilize its insane capacity. At full build-out, Epcot might be able to get 200,000-220,000 guests at a single time (every expansion pad used, all of the dead spaces reopened). DHS needs some major TLC. AK needs to keep growing and giving guests enough to do for a whole day.