It's painfully obvious you don't know the first thing about hip-hop because many of those artists do not talk about the same sort of thing. Tupac rapped about stuff that was virtually unheard of in hip-hop. Look at the lyrics for Brenda's Got a Baby, not only was that revolutionary for the time, it was a male rapping about it and doing it sincerely. NWA took on corrupt police in LA, got investigated by the federal government over it, and were even arrest because of it. They were bringing to light a very real issue of their time.
I don't know much about new rap so I can't comment much on those artists, but I do know quite a bit about early hip-hop and with many of those artists you mentioned, you're flat out wrong that they all rapped about the same stuff. Yes they had some songs about guns, girls, money, etc. but they also had a ton of songs that were very political and had a message in them. Some of them didn't resonate with people other than poor, inner city, blacks though.
Just because rappers don't play traditional instruments, many MCs used turntables as their instruments. When you're poor and living in the inner city with no real chance to go anywhere, you use what you can, which happened to be turntables. In some cases, they could get drum machines like an 808. But there are a bunch of rappers who are musically inclined and can play instruments. Hip-hop has its early roots in funk and jazz. Plenty of rappers continued with that and learned to play brass, bass, or drums.
Also, nevermind that Limp Bizkit really isn't hip-hop at all, but Nu Metal. There's some crossover, especially with their rock rap songs, but comparing Limp Bizkit to a group like NWA doesn't really make any sense. If you're going to compare them to a hip-hop group, maybe Run-DMC would work.