At the same time, you're no longer focusing on what makes each platform unique, and just giving them all a lowest common denominator. That's not really good either.
"This means I had to learn an entirely new technology stack"
Learning new things is good.
"Until Apple adds PWA support, I can't make as good stuff, and people can't use the better stuff."
This is absolutely wrong, and is just an excuse. You can make great stuff, and people can use it. You just need to put in effort.