Bad luck, you had the 737-700. The 737-700 is a good aircraft (if we talk about characteristics) but in deed it start to become a little bit out dated. It is leased since 2013 but was built in 2007. One was retired month ago. They plan to add Embraer E2 to replace their regional fleet but i guess also the last B737-700. B737-800 are better the youngest was delivered in 2017. They had a second hand B737-800 last year. But all others B737-800s were added direclty from Boeing. They have the Boeing Sky Interrior that you can see on Dreamliners.
I can just agree with you, B737 is a good planes, the old ones just like the versions 700 and 800 are old, but good, the airlines that still have them must care about their interior, the same is happening to Taag Angola Airlines, now they are refurbishing them, the B777 too, because it is horrible to see the interior of these planes, and just like she said, it is a gamble, tis trip you might get a good plane and the other a disastrous.
