People have been complaining about laziness in language and "dumbing down" language since language has existed. It's nothing new and it's not happening at a different rate than before. The perceived degredation of language is not, and has never been, a real thing. It's natural and unstoppable language change. It's the reason you can't understand Old English, and why Hindi, German, Spanish, and Russian are different languages from English now.

That being said, things like this theoretically could help to increase literacy rates significantly in populations with low literacy (in a similar way Simplified Chinese script along with Chinese education reforms drastically improved China's literacy rates) – and most of the US has surprisingly low literacy (about 54% of adults have low English literacy and 21% are illiterate) – or for people who aren't proficient enough readers to gain anything from reading something of such a high level. Reading should be accessible to as many people as possible, not gatekeeped. It would be far better as some sort of "annotation creator" though probably, if your goal is more literacy.

Of course, you shouldn't rely on something like this by any means. But it's not bad for a lot of purposes, we shouldn't beat uneducated people while they're down. And either way your literacy really doesn't affect your "stupidity", although a lot of resources with knowledge you might want will require a certain level of literacy.

Linguists aren't behavioral psychologists or K-12 educators. Being challenged by unfamiliar language is an incredibly important experience in developing reading comprehension. It's not that a bigger vocabulary makes you smarter, it's that the process of understanding more complex language helps you both understand and formulate more complex ideas.