I honestly don't understand how people can think the Earth is flat in 2023. You can see it for yourself. Go to the coast of a sufficiently large body of water, and try holding a ruler up to the horizon.
I think at this point, it's more a lifestyle and less a theoretical argument.
Yes, a flat earth doesn't stand up against science. But also, for most people it doesn't make a difference in their day-to-day life. So they have little to no incentive to ever tackle that notion.