I currently work in this area (web accessibility) and am just repeating what is commonly understood. When considering what WCAG criteria cover (which is not even everything that could pose a barrier to people with disabilities), most failures to meet the criteria cannot be identified by software alone.

For example, the classic I would say is not whether an image needs an alt attribute or not but whether an image's alt attribute value is a meaningful equivalent to the image in the context where it appears.

I'm not sure what kind of "resources" you're referring to. If you mean computing resources (CPU, RAM, etc.) standard, contemporary computers do seem to have enough for current assistive technologies, one doesn't need to buy a higher end computer to run them. If you mean OS resources for supplying assistive technologies and accessibility APIs, mainstream OS's are decent but specifically for screen readers there's a lot of room for improvement.