First of all, I disagree with S+ Landorus on the grounds that it doesn't have the same impact on the metagame as any other S+ Pokemon in any other format, but your arguments against it are just wrong.
Name a Lando-T "counter" and I'll give you a viable set that breaks it. Skarm? SD + Rockium, Smack Down, hell you can even run Gravity. Tang? Flyinium-Z. The closest thing to a Lando-T counter is an opposing Lando-T, and even that gets 2HKO'd by HP Ice or cleanly OHKO'd by +1 Z-Fly, no rocks needed. Nothing can safely switch in against Lando-T until you know the set it's running, this is part of the reason why it's so dangerous. There are several viable sets it can run and several variations of those sets it can run.Lando-T has hard checks and counters, and S+ pokemon should not. B
S+ is reserved for Pokemon who have an over-centralizing effect on the metagame, not "absolutely broken mons that can sweep entire teams". P-Don in Ubers is the classic example as its mere existence invalidates tons of otherwise viable Pokemon, and it's basically a necessity when creating a viable Ubers team. Lando-T isn't S+ because he doesn't have the same kind of effect on the metagame, not because he struggles to sweep teams or whatever.absolutely broken mons that can sweep entire teams
Uh... What? 2 of the 4 things you mentioned get outsped and smacked by EQ, and Gren can't switch in on basically anything. Saying "X, Y, and Z can KO it, therefore it can't be S+" is a plain dumb argument. Fucking Golduck can OHKO P-Don and yet if you brought that up as an argument against S+ P-Don you'd get laughed out of the VR thread (rightfully so).What ABOUT MAGEARNA? Its Ice Beam can wreck Landorus, and so can both Greninjas and Heatran. Lando-T cannot be S+ AT ALL, Otherwise it would be highly overstating Lando-T's Abilities.