np
btw reasoning would be:
thornmail = you want to receive damage, which you can't really survive on a support's salary. instead, you want to maximize your utility, which is what frozen heart is for. cdr, as reduction aura, more mana, all things that allow you to do your job better while also providing survivability. ranuins can also work because of the active but frozen heart is probably better specially because of blitz's passive/mana costs.
that's a really low bar for a support, wouldn't say that tells you you have a good support at all
other clear tells of people not really knowing what they're doing: any boots other than boots 5 (maybe except on zyra?), getting red sighstone early, never buying pinks, buying ap (except maybe on zyra lol) and generally the position and the timing of their warding
a bit situational since sometimes buying ap makes sense and someone could be trolling rather than being bad (lol) and someone you don't even get a sighstone for a while, but u know, rule of thumb
but yeah not having your support randomly go do wraiths doesn't tell really you he's good