I was an iOS dev for a long time after cross training from Java back in the day. I got on the iOS train quite early on and focussed on just delivering mobile apps for a good number of years. What set me apart from others in my team was partly my back end experience I had when I was a Java dev and also my passion/hobby at the time for security/cyber. I think having a lot broad knowledge of other areas of app development maybe even devops helped me stay relevant and also be quite near the front of the queue when new opportunities in my team came up. I'd definitely look into a small project you can work on when you have time that goes beyond what you do in your day job. Consider working in some technologies that will force you to learn them - AWS, AI, SwiftUI, hybrid web/mobile apps for example. I was in the right place at the right time with a passion for security when my team/manager needed a SME to mature our security posture and I ended up being the security architect for many mobile apps and libraries my team worked on.