The problem is not that the WBs couldn’t deal with a dragon, the problem is that some fans actually expect ponies to be like the Power-Puff Girls and deal with giant threats.
 
The WBs’s performance made perfect sense because they’re just ponies. Sure, they’re flying proffesionals but in the end they’re still just flying ponies. What did the fanbase expect them to do? Crash against him like a flurry of colorful blows that he actually felt and knocked him over? They’re not the PPGs. If they tried hitting him they would hurt themselves more than it would hurt him. Heck, its debatable whether even an Alicorn could potentially beat a dragon, and people were dissapointed at the WBs for failing?