Lots of us (well, me at least) use fly because it's a bundled set of aws best practices that I could configure in aws if I wanted to, but I'd waste another week of my life. alb + various vpcs + autoscaling group + fargate + ecs + their super shitty vpn service to vpn to a console + rds + elasticache or... just type "fly deploy" and go from zero to live in 20 minutes.
That said, fly's deploys are flaky. I hope they get it fixed because the rest of the service is pretty good.