On migrations
There's two ways you can view a tech migration. As a rip and replace, or a fresh start.
I've done both, as each have their use cases. The former comes into play when you're mostly concerned with keeping the Rube Goldbergian array of internal systems and tools from collapsing with the switch. The latter comes into play when that collapse will have no material consequences, or your systems lack the complexity for a collapse to be all that likely.
While part of this decision is circumstantial, I think it's mostly a decision based on attitude. If you view a marketing automation system migration, for instance, as a chance to start fresh, to trim out unnecessary fat and focus on building things right from the ground up, you'd be surprised how many "dependencies" melt away from your migration plan.
But if you view every existing system and process as equally valuable and worthy of maintaining exactly as before, you're more likely to take the rip and replace approach. And in the process, you may bring a lot of extraneous programs with you.
Increasingly I lean towards the reinvention of a fresh start with the migrations I'm involved in. Marketing is defined by reinvention, In teams, creative, and strategy. Why not adopt the same attitude with martech?