I also thought about just using search. But trending topics let me know if something important is happening when I'm not aware. I still think it's valuable at times, while I also think it may be spammy and should be improved.

I think its low signal to noise ratio makes you ignore it, which is bad. But I think instead of just removing it, spams should be prevented more effectively. Because I know "trending" concept is useful when it works. HN, Reddit and some other aggregator sites have homepages with trending content, of course with varying degree of success.