As a client, you might think web design comprises things like a homepage and a few interior page layouts, but web design is so much more. What about call-to-actions, buttons, and images? What about design flow? What about your navigation, headers, footers, and any side elements for up-selling products? Basically, design includes all the elements of your site, and they all need to flow with your color scheme and business idea.
There are exceptions to this title; many private clubs and religious organizations may not be bound by Title III. With regard to historic properties (those properties that are listed or that are eligible for listing in the National Register of Historic Places, or properties designated as historic under state or local law), those facilities must still comply with the provisions of Title III of the ADA to the "maximum extent feasible" but if following the usual standards would "threaten to destroy the historic significance of a feature of the building" then alternative standards may be used.
This is the reason why I think web design firms have to position themselves as solution providers and not just web guys/gals. A client doesn't need a website, they need sales. The website is just part of that solution but it's not the solution and unlike web design, service like email marketing automation, SEO, and PPC requires an experienced professional.

The ADA has four main components: (1) requirements for maintaining medical records and requiring medical testing, (2) an employer must reasonably accommodate disabilities, (3) an employer may not discriminate against an individual with a disability, and (4) an employer may not retaliate against someone who opposes discrimination of participates in protected activity.
This title is designed to help people with disabilities access the same employment opportunities and benefits available to people without disabilities. Employers must provide reasonable accommodations to qualified applicants or employees. A reasonable accommodation is any modification or adjustment to a job or the work environment that will enable an applicant or employee with a disability to participate in the application process or to perform essential job functions.  

The ADA states that a "covered entity" shall not discriminate against "a qualified individual with a disability".[12] This applies to job application procedures, hiring, advancement and discharge of employees, job training, and other terms, conditions, and privileges of employment. "Covered entities" include employers with 15 or more employees, as well as employment agencies, labor organizations, and joint labor-management committees.[13] There are strict limitations on when a covered entity can ask job applicants or employees disability-related questions or require them to undergo medical examination, and all medical information must be kept confidential.[14][15]

There are many ways to discriminate against people based on disabilities, including psychological ones. Anyone known to have a history of mental disorders can be considered disabled. Employers with more than 15 employees must take care to treat all employees fairly and with any accommodations needed. Even when an employee is doing a job exceptionally well, she or he is not necessarily no longer disabled; employers must continue to follow all policies for the disabled.
In an August 2016 case involving the University of California Berkeley, the DOJ ruled that the public university was in violation of ADA Title II (similar to Title III but it instead applies to government organizations) because their YouTube channel’s videos didn’t include captions for hearing impaired visitors. The DOJ found this to violate the ADA as deaf users did not have equal access to the online content.
As I mentioned above, under each WCAG 2.1 principle is a list of guidelines, and under each guideline are compliance standards, with techniques and failure examples at each level. Some guidelines include only Level A items; others include items for multiple levels of conformance, building from A to AAA. At each stage, you can easily see what more you would need to do to reach Level AA or AAA. In this way, many websites include elements at multiple levels of accessibility.

I own a medical practice in California with 5 employees. Since I have under 15 employees am I exempt from needing to have my website comply with the ADA? I know that my physical practice is exempt from ADA policies regarding employment (under 15) but I don’t know if that extends to websites. My website is not an important part of my practice and I don’t really want to sink any funds into it if I don’t need to.