I'm going to differ here.
I'm definitely far less experienced than you are (closer to 300 battles, around 200 of them rated), but many times I have tweaked predictable Pokemon in order to make them either radically different or designed to brutally rape their counters even though they're barely feasible (yawn-induced FP Snorlax, HP Ground Skarmory, Endure-Salac-Explosion Metagross). Other times I have used relatively unused Pokemon to catch troubling Pokemon by surprise (Tropius in favor of Exeggutor due to its obscurity). With the knowledge of what's currently in vogue, you can create WTF-inducing movesets.
These movesets will spawn a WTF-look upon your opponents immediatly, whether you send them out now, 2 months ago or 9 months ahead. There's a a difference (actually, I don't see a similiarity) between using unexpected movesets and taking into account what is used at the moment. I see posts like "well Raikou use has definitely gone down since 2 days 13 hours 20 minutes and 15 seconds ago" quite often and I honestly don't see how you would know this, considering there's no NB statistical database anymore, and if you go by what you see, you have a flawed argument. Why? Because
- you could have been battling the same group of people over and over, who have a certain preference
- let's say someone challenges you. If you accept, you see 6 pokemon and add them to your memory as "pokemon you saw" and add 1 to how often you've seen. But if you refuse, you won't see them. Does that mean that if you don't battle this person you can say they are "used less"? Yeah they are used less because they've been in battle less because you refused...but that's not what this is about if you catch my draft.
I'm sure almost every skilled player bases their team partly around countering what's currently popular while taking it a step further and aiming to counter those counters with their own Pokemon. (weird wording.)
You're either not saying I'm a skilled battler, or you are just generalizing. Countering Pokemon that counter your Pokemon is from all times. But seriously: let's say Blaziken is a really impopular Pokemon despite its tier status (kind of a contradiction, but I do acknowledge the existance of certain trends). Would you not bother putting a Blaziken counter on your team, because it is "not used nowadays"? You're going to get swept if someone goes out of their way and does, and that's why it's dumb to go by what you see or what you hear from what is used.