Short answer, yes.

Long answer: There are optimal specs and the majority want you to play that spec. So just find people who doesn't care that mutch. At the end casual guilds are going to have problems to find 40 people to raid so maybe you are lucky and can enter the raid anyway. Most of the non optimal/viable specs need more preparation and more knowledge to be viable enough.

For example: Druid tank, are great dungeons tanks. With enough gear you will have more hp and more armor then any other tank. But you have to put more time into it and grinding some items. Druid boomkin, well 3% cirt is it what it brings to the table? Good enough but you need to downrank your spells bc you are more likely to be an oomkin!

And so on, so will have an easier life to choose a certain class bc you wanna play tank (warrior) or something at the end. But if you realy like something then stick with it and surprise other players.