What does "locked in the Apple ecosystem" imply? Apps that don't have a satisfactory equivalent on Android, integration between Apple devices or general usability/user experience?
Other than that, nothing should really keep you "locked-in" on iOS. Not even iMessage. You can use WhatsApp or FB Messenger with friends or family. It's not a big deal.
https://www.android.com/switch/
https://www.apple.com/iphone/move-to-ios/
I still like iOS better and don't intend on switching but the only "lock in" I feel exists is the years of sunk cost I have in purchased apps I still use.
I would disagree about iMessage though. I have older family members on iOS that would not use another messaging or video chat app. Our chat experience would simply degrade to stock SMS.