Depends what you mean.
It seems beyond reasonable doubt that all models (understandings involving reality) are wrong, and some are less wrong than others (reality does in fact seem to be that complex, more complex than we can possibly understand in detail).
The idea that the earth is flat is fine if you never go further from home than about 50 miles, and never want to do anything more complex than build a house from lumber and nails. At that scale it will work to explain most things. Carpenters still use it today when building houses.
It will result in a few ideas that are still too common today, like the earth is at the center of the universe and everything revolves around us, and we are something special (like God’s chosen) because of that.
If you travel much further than about 50 miles, and you measure things to the accuracy of an inch or so, you will start to notice discrepancies.
If, like me, you live by the ocean, and have mountains nearby, it is not difficult to get someone to take a boat offshore, and measure how far away they are before they disappear, from different heights. That will tell you the world is roughly round, and give you an answer for how big it is that is reasonably accurate (is close enough to what is published in the encyclopedias to convince anyone of their accuracy).
Once you get the idea that we live on a ball of matter that is spinning, and it is going around the local star (our sun), and that is only one sun in a collection of a hundred billion or so orbiting around each other in our galaxy, and that is only one galaxy among billions, then the idea that we are super special because we are at the center of the universe and everything revolves around us has to go away. Some people like that idea more than reality – hence most of the nonsense about flat earth.
We now know, beyond any shadow of reasonable doubt, that this planet we live on is largely molten rock, with a thinish (from 5 – 50 miles thick – depending on where you are) skin of cooler rock on the outside that is organised into plates that move around, and some of them fold under others and go back down into the molten stuff, remelt, and give rise to mountains and volcanoes and earthquakes (they move about the same rate our fingernails grow, and give us earthquakes like the one we had here in Kaikoura 3 years ago, that took out all our road access to other places). It is all fascinating, but in order to be fascinated by it, one has to show a bit of humility, and get off the ideas that one can know anything with perfect accuracy, or that we are at any sort of special place in the universe (geometricly speaking).