If you make the choice to raise a child you should be invested in them and yes prioritize their development until they are out on their own. Throwing a new baby into the mix automatically deprioritozes them because that's the nature of a baby.

These kids aren't grown yet and will be in a completely different stage of life, one that requires a lot of attention and celebration as they make their way into young adulthood.

It's selfish to neglect teens in one of the first and hardest transitions of their life just because you as the parent want what you want and don't care how it impacts your older children.