Just because you have a gold plated, bespoke pencil won't make you Shakespeare though
I've seen this sentiment expressed over and over and I totally disagree with it. Not picking on you in particular, but I keep reading it "Composer X can make a bucket of nails sound like great music." If that's the case, why do many of the most widely admired composers in Hollywood buy new samples?
When I started, electronic music sounded awful -- samples were terrible, really; extremely limited in the articulations they could produce, and many of the sounds themselves are / were thin or soulless. No matter how much time you lavished on them they could only execute a limited number of ideas, and those poorly.
And the thing is -- if you work in media, the approval process means that you're stuck with the limits of your mockups to a great extent. Unless you're John Williams.
Nearly every cue I write has to be auditioned by someone, often a lot of someones, and if it sounds unconvincing, it gets the "I just don't know..." "not sure...." and I have to rewrite it.
And it's not just that, feeble samples affect my creative side too. Listening to work I did 10 years ago or more, I hear myself constantly disguising it with orchestration tricks to mask the shortcomings of the samples or synths. Still do it, really, though things sound infinitely better. I'm working on something right now and even with the 10,000 samples I have I still can't execute what a 26 person orchestra can do.
Why buy anything new at all?
What I'd love is a REALLY compelling set of samples so that I can actually write a solo line that is even 40% as good as the real thing. A good cellist or oboe player or anything, really, can make you feel something valid and non-trivial, whereas most solo samples just can't quite get there.
Simplicity and boldness with a single idea sometimes says more than a full orchestra, but weak samples can't execute that.
Great samples won't make you Beethoven or Eliot Goldenthal, no, but they can open doors, creatively and professionally.