Is it a valid or acceptable practice to develop a separate page to meet accessibility requirements?

I recently visited some websites that seems to be using either deprecated technology (e.g. Flash) or contain a lot of complex front end javascript code to create the interaction of the user interface.

Some of these websites provide a link or button that takes you to a accessibility mode page which strips all the unnecessary features and provide just the content that is optimised for screen readers and provide other accessible features (e.g. keyboard navigation).

With accessibility being such a big focus today, and inclusive design slowly being incorporated into many of the standard design systems, is it still seen as an acceptable practice to provide a separate page to meet accessibility guidelines (i.e. WCAG 2.0)? Are there other reasons why this might be a better strategy/option in the current design and development culture?