What makes you think the online is worse now? The only thing that has changed is that people now have to pay to keep playing. It's not like people who pay are more likely to have bad connections (you'd expect it to be the opposite, if anything).
You're likely just running into some bad luck. I've had quite the opposite experience lately.
I watch a ton of streams, and the majority of the ones I watch talk almost every day about experiencing the same thing since about a weekish before paid online started. That's hardly a scientific study, but neither is your individual experience.
And you don't know that the only thing that's changed is people now have to pay. It could be or maybe some stuff is happening behind the scenes that Nintendo hasn't told us. At any rate, my experience has been much worse since paid online and it was honestly solid enough (aside from match making) before paid online.
One thing I'll mention is that half the world has been rocked by various tropical storms for the last month+. This could be affecting infrastructure, including online infrastructure. I'm going to monitor if online gets better once trop season is over. And it would also make sense that Europe would be the least affected by changes in online quality as Europe is the place trops least affect.
So basically, I'm hoping it's either Nintendo working on stuff behind the scenes that will eventually lead to better online or it's weather-related issues completely out of Nintendo's control. But, like, I don't have a ton of faith in it being either of these things. It's just wishful thinking on my part.