You're right, it is a different game since you last did well with him in season 3 and 4.
People aren't too stubborn to buy pinks when they are the only wards in the shop and everyone is buying them. Moreover, anyone can get vision of half the map with the new blue trinkets giving you a permanent ward every minute, and they can do it safer and with much larger vision radius.
It's not mathematically possible to shroom the enemy jungle for full vision with a 5 minute trap duration. Maybe at 40% cdr at level 16. But at that point if you have free reign to run around the enemy jungle without dying, you're already dominating the game.
I would normally agree that Teemo wrecks marksmen, but 5.22 gave them far better access to abilities that blind does not affect. In fact, the only ADC Teemo is particularly strong against is Vayne.
As for account-checking, I agree that a player's win rate doesn't mean everything. In your case, you're making a specific claim that Teemo is strong, and that should be supported by data. The overall data (not just yours) does not support your claim, so I check to see if you've had good results that would support your conclusion. You don't.
If I say "Zyra is an amazing support pick!" I get lots of shit from players because she's objectively not an amazing pick. But if you account-check me, my opinion makes more sense. In around 200 ranked games my win rate is 59%, far above average for Zyra support. That tells you something about what is informing my statement. I think she's good because I get good results.
You're just saying Teemo is awesome when the data say otherwise, your own S5 stats say otherwise, and you don't have any experience playing Teemo top or mid in 5.22. What it comes down to is that you're wrong. Be content to say "I like Teemo" (which is fine) without deceiving yourself into believing that he's actually good at the moment.