Clever people are still being made. We still have people training to be doctors, lawyers, architects etc. But the world's population grows ever larger, so obviously there are going to be more stupid people born. The share of stupid to clever might remain the same, but the absolute numbers will be higher. And the numbers of stupid people have always way outstripped clever people. So yes, in a way you're right. With the way that population growth works, and the distribution of intelligence (i.e. more stupid people born than clever), there have, quite literally, never been as many stupid people in the world as there are now.
Add to that, the internet and social media is almost certainly replacing reading books to some degree, maybe a large degree, and this is a significant factor in levels of stupid. If people don't read, or read as much, they are not exposed to complex ideas that are clearly written and properly spelt.
Younger children are not supervised after school as much due to the out-of-control costs of living and housing meaning that both parents need to work full-time. So there's less reading and studying after school, probably.