Collaborations on the album doesn't mean they're out of ideas. They just wanted to collaborate. Creativity isn't a finite resource, you don't just "run out" one day.
Also, I disagree with your assessment of their work lately. MTM/ATS were Linkin Park's best albums to me, but it's not like LT/THP/OML are bad albums by any means.
Different people have different tastes. On this site alone, I've seen people who think HT/M are the band's weakest albums, and I've seen people who think HT/M are their only good albums. It's all subjective, and it's what makes this community so interesting. Trashing the band though and insulting their work without being constructive is just a waste of time, though.
@GraDoN What you said is also subjective. You say the band isn't talented, as if that's just an unspoken fact that is indisputably true. There are literally millions of people who would disagree with that statement, though. I am one of them. I feel LP as a collective, are a talented band. Do they have misfires? Yes. Any band that switches up their style as many times as they have are bound to have a couple of misses, but as a whole I think they are an innovative band that's very open to change, and almost always pulls it off.