You have a interesting way of evaluating "happiness"

Check out the highest voted post. at 111 up-votes, it out-weighs all of what I would consider as clearly positive vote (e.g. I love sage, sage is 10/10, buttery smooth)

"Sage feels like it should have a more robust DPS kit and a different function for kardia. I don't really feel the job's core idea much at all - it heals when I DPS but my DPS kit is extremely limited and I'm always DPSing so it just feels like a regen in practice. There's no DPS move I have to save or think about, I just pop them off cool down

It's stylish though. Haima and snap shielding are fun and having to activate eukrasia tickle my brain."

When I look at this one, it doesn't come off as "happy". I can also find others which are more negative in tone.

Agreed, there are also positive ones , looking at them quickly I found three that totalled up to about 75.

So a quick review would tell me that it's not so much a "so many people are happy" but that it's a mixed bag. Yes, some people do like Sage, and some really like Sage, but a significant amount, possibly a majority, have issues with Sage. It's not what they expected, they may like some aspects, however they want to changes.