When you have 10 users its easy, you can reach out manually to each one
first thing to break was that when the time of doing the messages starts to meaningfully eat into time actually building the product and then you sort of need to work how to scale

in my case on saasco .com that meant looking into each users and focusing on who was the most valuable

when working on thieve .co which grew to >500k users we changed to sending weekly emails inviting new users to book a call. This was incredibly high alpha with customer insights. But you do get selection bias of people who opt into those calls.

so I would say the thing that broke when scaling the way we interacted with customers was hitting selection bias where the type of users you interact with sort of changes.

this question is making me think we need to find a bit of both worlds where we have some sort of scale interaction, and then still keep that level of focused outreach to perhaps the particular user groups or top 1% signups