Is doing something for yourself really working for free? That's an interesting take. But I can understand why you don't want this for yourself, so enjoy the page in all its splendour as it is already!
CSS is explicitly designed for you to apply your own user stylesheet. That is exactly what it envisions you doing. If you don't like web technologies you might want to question what you are doing on the web. However, the web also encourages sharing, so no, theoretically once one user has created a user stylesheet they would share it with others so there would be no need for everyone to create their own, unless they had alternative tastes.
I mean, if it really bothers you you could fairly trivially apply picocss or whatever to it using a user stylesheet. That is so little effort that calling it working for free would be disingenuous to say the least.
For people in the future who want to apply the centered viewport classless version of Pico CSS, just apply the following in Firefox's Style Editor (F12 to open DevTools, then click on Style Editor; click on the + sign to add a new style):
Browser vendors have really dropped the ball in supporting CSS, which is no doubt how we get comments like the above. Firefox is likely the least-worst offender, but as you point out still needlessly complicated for what CSS considers to be a foundational feature.
A closer analogy is going to a gas station where a microwave is offered to heat up any food you purchased. If you don't want to heat up the food, cool. If you expect the food to come hot you're in the wrong place.
Except in this case it's a gas station that only exists for the benefit of its owners and there isn't any food for sale. The owners have graciously said you could still use the microwave if you'd like, though.
