Right now we're doing okay, but we haven't seen whether the planet can support us long term like this (or more accurately, whether 10 billion people can adapt successfully to a world we've changed).
Already, we're worried about the decline in pollinators, frogs, insect splatter, coral reef loss, and tropical forest deforestation. What do you think just that looks like in a few decades with 2-3 more billion people?
The human population is ultimately independent of the biosphere through technology. And, in fact, some of the worst impacts on the biosphere are when we lean strongly on the biosphere to provide for us (for instance, cutting down forests to provide fuel and to clear land for inefficient farming practices vs using solar/wind/nuclear to provide energy while using dense and hyper-efficient farming practices).
Technology has huge returns to scale, and technology is how we're already able to handle our current population. So I'd say we are indeed better off with more people than less, particularly if we reduce agricultural land usage (which we're already doing) and switch to non-burning energy sources (so no fossil fuels and no biomass). An effectively vegan diet (either truly vegan or using lab-grown meat and dairy and eggs) would, by itself, drastically reduce both our reliance and impact on the biosphere. Vat-grown staples (think specialized microalgae) substituting for field-grown staples like corn or wheat or soy would further drastically reduce our impact.
The Earth ought to be a garden, but not one empty of people! And a human society without children would be some kind of dystopia.
It's a good thing for some people to choose to pursue other things and not have kids. There's plenty of room for both kinds of people. But choosing to have kids in today's society is a huge challenge, and society as a whole should help women (and their partners) who choose to have kids. We should, as a MINIMUM, make healthcare free for children and mothers (and really everyone). We should also make it easier for mothers and fathers to balance family and work. Women shouldn't have to choose between their career and the normal (and very important) decision to bear children.
And we can't get too far down this road before asking the question: Are humans fundamentally a bad thing or a good thing?
This is obviously subjective. But if we say some things have intrinsic value, such as the quantity and diversity of life, then we can make some progress:
From Gaia's perspective, if humans evolved, wiped out a bunch of species, then disappeared, then humans are like an asteroid. Bad at first, but ultimately just changed the direction of evolution, not the actual presence or absence of life.
BUT, if humans are able to go beyond the Earth and establish niches for life beyond Earth, then from Gaia's perspective, humans are a net-good. Sure, there's a lot of terrible habitat destruction as humans become a technological species capable of interplanetary travel, but now humans are capable of seeding life far beyond what other species have been capable of. Humans could create diverse, rich niches for life on other planets and moons that otherwise would never experience life. Humans would then be a net-good.
That becomes impossible if we just view humanity's impact in a zero- or negative-sum way. The more humans, the worse it is for life. BUT 10 billion may be just about the minimum needed to support a large-scale interplanetary capability that's able to establish a foothold for life to flourish across the solar system and eventually the galaxy. Therefore: have children! And reduce your impact on the Earth by eating smart and using efficient energy and transportation options.