Making your website accessible is a good business decision.
But is it required by law?
For a useful summary, check out this article from UserWay, the most widely-used accessibility solution.
As we read it, if your website is for a government agency or a "brick and mortar" business, we'd say "probably yes".
If not, chances are, it will depend on what a judge says, if you are sued.
But we aren't lawyers, so we suggest you talk to yours.