To give you some context, prior to this quote the author references the fact that there is a theoretical impending generational turnover that coincides with the fact that the shift to an almost entirely digital environment requires academic library workers to identify emerging needs of academic library users and develop services to meet those needs. The quote implies that because the newest hires among us are younger than us, they can help those they report to better understand how to navigate this new world and what it requires of us.
I have three things I want to say about this.
First, that's a lot of pressure to put on the shoulders of someone who just got hired into an academic library. Imagine that you're an early career librarian. You're in your first job out of graduate school, mostly likely with a lot of student debt. Depending on how much you learned in school or through internships, you may feel out of your depth in this academic environment. If you're a person with marginalized identities, you may already feel like you were hired as the token person to teach everyone about diversity and inclusion. Now imagine that your supervisor, or someone higher up on the library's administrative team would like for you to help them understand younger library users and what they need. Or maybe they don't ask you to be part of the conversation--maybe they just add to your job description that you'll be charged with developing new and innovative services to reach younger user groups. That's a lot of pressure, right? The best outcome in this situation is that your early career colleagues will feel overwhelmed with all of this responsibility. The worst is that they burn out because you're set them up to fail.
Second, demanding that your newest and youngest library workers help you "figure out" what the future looks like disenfranchises the mid-career and late-career library workers in your organization. It suggests that an administrator feels like those library workers are too out of touch with what younger users need and, as a result, don't have any good ideas. I am not a fan of the but we've always done it this way mentality, but I do think we need to acknowledge that both our new hires and our incumbent staff are capable of coming up with good ideas about how to serve the various user groups in our academic libraries. Early career librarians have the good fortune of being new to your organization and they can see your services with fresh eyes. Mid-career and late-career librarians have the benefit of having seen the context in which your services exist and the context into which you plan to introduce new services. Assuming (and, yes, this is a big assumption) they are open to the adoption of new ideas, they can offer constructive feedback and help you anticipate problems.
Finally, the future is not as knowable as you think it is. Yes, you can use present data to predict future trends. But your user community is not a monolith and its likely that by the time you build the services you think they want that their needs will have already changed. We have this problem in librarianship where we're constantly trying to outrun our obsolescence by trying to predict the future and create services to support it. That's not great because it keeps us from engaging with the present--with identifying the needs of our users as they are right now and expending our resources to meet them. Sure, look at gate count and study how users make use of your space. And use the data you gather to be the best steward of your resources that you can. But never get too attached to the idea of the future that you give away resources your current users need to build a future that your future users may never need.
All of this is not to say that you shouldn't trust the opinion of early career librarians when it come to creating and deploying services to meet the emerging needs of library users. You should. But do it by including early career librarians in conversations in your library about these emerging issues and listening to them when they talk. Placing the burden entirely upon them for helping to create the future of your library is bound to be problematic for everyone.