At this point, surely access to the internet is at least a utility, if not a human right. Olu has put together a brilliantly reasoned argument for just that, and how to go about building for a world where not everyone has access to digital resources equally.
Not having access to the internet is expensive, locking you out of essential services and a surfeit of helpful information.
It's far from being a "developing nations issue" either (though, to be clear, it is a huge issue in a lot of developing countries). In the UK, 10% of adults were considered to be "digitally excluded" in 2018; and yes, this is an issue which disproportionately affects women, people of colour, and people living with disabilities, whilst richer households are more likely to benefit from the web.
Marginalized people with insights to share aren’t hard to find when you start listening. They are your next users, your future developers, your fledgling marketing team. Excluding them reduces your options, your appeal, and your breadth of ideas.
Seek a broad range of opinions; hire inclusively; be proactive about improving and advocating for diversity; test your tools with a diverse audience in mind (screen readers, Pa11y, axe, Lighthouse, etc.); where possible, provide non-digital avenues to your services as well.
Web accessibility is not an optional extra. What inclusion looks like in practice will depend on your products, your users, and what you intend to achieve, but for it to be real and meaningful in any context, it cannot be an afterthought.
The fact that this kind of engineering is commonplace on the internet doesn’t make it OK. It just highlights that the way we have built the web is fundamentally broken.