She's still running around in Yoga pants, so the sex appeal is still there, but the pose (in addition to just not looking very good) speaks to a self-aware flaunting of sexuality in a way that seems at odds with Tracer's 'spunky teen sidekick' persona. The vibe I get from what gameplay/videos/trailers/animations I've seen is tracer is the sort to basically have had that same costume since before it could possibly count as sexy on her to anyone that doesn't have nightmares about Chris Hansen, and never changed it as she grew up. Not necessarily naive about her appeal, not an Ellie Mae situation, but a sort of accidental sex appeal.

I'm not saying any of this is canon, but that it's the impression I get off what I've seen so far of the characters.

If you read the original complaint, and Blizzard's clarification on why they removed it, the core is that the pose is out of character for that character. In fact, the original complaint even mentions more sexuallized heroes and how their flaunting of what their momma (or a skilled surgeon) gave them is totally in character, for them, but not for Tracer.

All of the 'oh my god! They removed the bootie, censorship!' Complaints are feeling, in light of the actual original complaint and Blizzard's cited reasons for the pose's removal, more like children stomping their feet that someone might create an attractive female character who doesn't deliberately flaunt it.