So are they bad players even if they keep everyone alive without risking the well-being of the party? I would be slow to call them bad because they can clearly do their primary role just fine. I would merely call them serviceable. Like a boring cheap car. It gets you from A to B but it's nothing special. I wouldn't bring them to savage for similar reasons why I wouldn't bring that unremarkable car to a F1 race. But for normal stuff both are fine even if they're not ideal.
A bad healer is someone who either cannot heal a normal combat situation effectively even when they try, or someone who plays their class as if they're in a savage team who carefully planned their healing spells and mitigation so they could pump out as much dps as possible, even though they're with a pug who made no such plans...and they continue to do so even though it's clear that more healing needs to be done.
Both of these are far worse than a pure healer who can keep everyone alive. Yes it's annoying when the healer does no dps when they clearly have time to, but healer dps is far from a requirement in normal mode content. I prefer to do things a bit slower and be confident that everyone will stay alive, rather than be stressing out because the healer acts like only mobs can lose hp. These healers are the bane of my existence when I play rdm. It's annoying that I have to stop dpsing and toss out heals to keep the tank alive because they're too busy pretending they're an all-star savage player to do the most basic requirements of their role properly.
The few times I have been curious enough about these players to look them up in fflogs, each time none of them had anything resembling impressive savage kills as healers, if any at all. Which is why I say "too busy pretending". Likely they read a healing guide intended for top tier savage raiding, and they lack the presence of mind to realise that this particular playstyle can be destructive if you just blindly do it all the time. This is definitely a definition of a bad player. Someone who copies what top tier savage raiders do without thinking about whether it's appropriate for the given situation or not.