From my experience, everyone is generally very understanding in game, especially towards new healers who are only just learning. The people who are called lazy are the ones who are at level 70 and experienced and choose to do nothing (when no healing is required) when they could instead choose to be helpful and DPS. The healers who stand still, jump around or /dance while watching the rest of their team work. These are the players that get on other players' nerves, not the ones who are trying to play their job well and be helpful to their party but are new and only just learning (or have other things that prevent them from playing the job fully).
When I see a healer who only heals in game, I say to them something like "hey healer, don't be afraid to also DPS a bit!" or "could you please use some DoTs / Holy / Gravity when no one is in any danger?", and then do my best to be supportive and offer advice if needed (usually I only offer the advice after the run is finished so they can consider it for their next run though, so they won't feel too pressured during the run, like today when I asked an AST to do some DPS in Aery and they proceeded to Gravity spam single target boss fightsI let them do their thing but after we were finished adviced to use DoT and Malefic on single targets and save Gravity for groups).
I will never just blindly kick someone for not DPSing and I've never seen anyone blindly kicked for that either. I also never kick someone if they say that they're new and not comfortable enough yet to try DPS, although I do try to encourage them to try. The only times I've seen healers being kicked for not DPSing (some of them initiated by myself) have been when the healer has replied to a request of participating in DPS with "no I won't, it's not my job", so it's been a question of refusing to cooperate with your party.