FTP has nothing to do with resiliency. It has to do with capacity. You want to go faster for longer? You need to have the aerobic capacity and muscular endurance to do so.
Also – and sometimes this needs to be said, and it’s not meant to be rude – but if you only have a specific amount of time to exercise (as is the case with most of us), and you’re dividing that time between a number of disciplines without committing the necessary work to getting better at cycling, then you’re unlikely to get that much faster or raise your FTP. At some point the volume needs to go up, the intensity needs to go up – or both – or you’ll sit around the same plateau. As was the case with me.
If you wanted to get a higher max bench press in the weight room, but only had time to do push-ups for 15 minutes a day, there really would only be so high you can go without getting in the weight room and moving the iron.
I think most of the triathletes on this board would tell you that they could all be MUCH better cyclists if they devoted all their time to cycling vs. splitting their time between the other disciplines.
As always, good luck.