For me personally, there were more good books a year back then than there are now, but then there were a lot more books per year back then anyway...
As for original characters, Diane Duane & Peter David wrote fantastic original characters. PAD in particular wrote some of my favourite original characters, and fleshed out numerous bit characters from the tv series. Calhoun, Janos, McHenry, Burgoyne, Kebron, and so on. These days I can think of Ree, some of the Voy Relaunch and some of the Vanguard characters that I like. Ent-e, Aventine & most titan regulars I don't particularly care about.
So not seeing much of a difference there. Also, most of the books you listed were rubbish anyway - some of the shatner ones were good(the earliest ones like eden and return), but all the day of honour books I can remember were rubbish(although the tng one had an interesting moral point to it at least), the original dominion war books were rubbish, and I don't even remember badlands.
One difference I do see sadly is that characterisation of Kirk, McCoy & Spock is generally far worse these days then it used to be. No idea why that is.