writing really good (sounding) stuff is all about personalisation, and that is basically achieved by genuinely playing with what you got lying around. i think that's a perfect term. you play with your stuff, and it gets as involved as playing with an instrument, only that it works a bit different with sequencing. maybe you're more diligent or disciplined or nitty gritty or chaotic and happy go lucky about the way you play, but it all results in immersion and flow, and then cool stuff happens.
i have trouble with pristine, complex libraries and such. i feel like they're playing me rather than i play them, and my buyer's remorse extends to me even feeling that i'm not worthy of them, because i don't get much done with most of them. i'm happy with the few big products i ended up using a ton. otherwise, i really dig soundfonts and such. because you HAVE to personalise them, else it sounds like crap.
who am i to talk in this thread though! i never composed for anything noteworthy, i'm just verbalising my ten+ years of VST related OCD, buyer's remorse, and creative ruts here
so, generic advice resulting from this questionable experience: if you buy something big, research it well beforehand, be certain about it, and then try to love it and make some beautiful shit with it before buying anything else! even though it's virtual, it's very similar to the guitar standing in your bedroom or whatever. you either love it to bits, or it may become this thing loaded with frustration and missed potential.