It doesn't seem like you've actually moved away from using TCP.
Maybe it's just too low of a layer for your needs?
In the context of 2023, this is a defensible position. I can quibble, but it's defensible.
However, are you sure you want a 1974 take on a "message based protocol"? Trust me, you're not getting SCTP out of that, in a world where having two streams instead of just one is a noticeable resource impact. Heck, even by the 1990s there were still a lot of really bad things coming out of the world of "message based protocols".
You wouldn't be here in 2023 with a message-based TCP. You'd be here in 2023 with some other protocol having become the foundation of the Internet, and it wouldn't be "message based" either. There's no option where someone in 1974 is building with the nearly 50 years of experience that haven't happened yet, and I'm not going to grade TCP on that basis personally.
I personally stopped using raw TCP because it is almost always the wrong solution. If I need a bare bones protocol where I want to send raw bytes I now always use websockets because they work exactly as they should.