It's not a 'good thing' to deal with piles of legacy spaghetti code with no method to it's madness. Sure if you've been coding UIs for years, I'm sure we'd work fine together. In my experience, coding designers, have not been experienced coders.
Just because someone isn't top of the line doesn't mean they should be dismissed or frowned upon.
Further, if it's something mission critical, just politely ask them if you can work on it to ensure its quality.