Yeah, that's true. Flex, however, dedicated some efforts to accessibility. But, developers didn't want the components Flex had to offer. Custom stuff almost never implemented accessibility interfaces.

This also impacted how search worked. At the time of the sale of Flash to Adobe, either Macromedia before the sale, or Adobe right after the sale donated a "headless" version of Flash player to Google in hopes that they'll make something of it, something that'd help with searching within Flash applets... I don't know the details, but I know that the project essentially failed to even start. That player never received any updates, and Google wouldn't search inside Flash. I think, the real reason was that it was just way too hard to search inside Flash due to the very dynamic nature of these applets. Pieces of text would often appear in very small chunks, random order, impossible to tell if visible or not etc.

With HTML and JavaScript, eventually Google faced the same problem, and that's how they came up with Chrome. For some reason they decided not to make their own player.