Signal depends on big tech like 99.99% of other services. You literally host your code on GitHub, which is a Microsoft platform.
It's not cool to fight with someone who has the same mission as you do. You have a different approach? Cool. Most people will still use Signal, because it's more convenient, proven, well supported and the tiny ethical trade-off is negligent.
I don't eat meat, but I don't go around fighting people that give ham sandwiches to the homeless.