Exactly this! Current shop has a crufty in-house monstrosity with a weird history. All due to someone deciding that the stack had to be Python/Django + Backbone

Exactly this! Current shop has a crufty in-house monstrosity with a weird history. All due to someone deciding that the stack had to be Python/Django + Backbone.js + jQuery. Not a bad stack, but the development team was a group of PHP developers. Rather than go with something they all knew, the leadership decided that switching stacks and having the entire group learn Python with the CMS/CRM/Fulfillment system being their first professional project was the way to go. What resulted was a misshapen monstrosity. Plenty of good ideas, ruined by limitations in understanding of the stack they tried to implement, and further hampered by a lack of good direction and herding of the team. The stakeowners of various bits were allowed to snag their pet developer and lean on them until their "feature" was implemented, with little to no cohesive architecture in place. Perfect is the enemy of good. There are dozens of frameworks because they all have their uses. Stick to what you know, and let that guide you. If you have a desire to learn a new stack, go for it. But don't pick one because someone else says "it's the best".