Few on the list are modern writers. A few of my favourite stand-alone writers are:
Guy Gavriel Kay (fantasy), though he's written a trilogy *and* a sequel (sort of)
CS Friedman - famous for a fantasy trilogy but I prefer her SF stand-alones. And there is now a sequel to one of them...
I confess I *like* series, when done well. A properly designed series should read as stories within a single broader story arc. I also like stand-alones or shorter series within a common universe where past characters can intersect.