Welcome to the site.
The bend itself is not really a deal-breaker, but we would want to minimize the amount of bends as much as possible. The first thing I would do is replace that flexible pipe with smooth metal vent pipe...or at least the stuff that's called "semi-rigid". You can find fittings to make that tight turn. But have you checked to see if the Mfr built in alternate ways to hook up the dryer? Some have a panel that will allow the unit to be vented from the side as well as the back. And although it's hard to tell from the pic, you may be able to get a straighter run by using the alternate hookup. Just as important, where and how far does the vent run once it goes through the wall?