Email might be a neutral tool, but not using a tool like LinkedIn is worse because you're restricting your hiring pool to immediate connections. For all its warts, LinkedIn allows job seekers to connect with a wider range of jobs and job posters to connect to a wider range of potential candidates.
The answer isn't to double down on a "it's not what you know but who you know" world.
Most outside recruiters are terrible, we can agree on that. It's a two-fold problem, they give you poor candidates and harm the reputation of your firm by leaving a poor impression of you to them. I'm looking for work right now and had first hand experience of this recently; I don't know if I should feel sad that I didn't get a job that sounded perfect or happy that I dodged a bullet because if the candidate experience was so bad, what would working there be like?
I dislike LinkedIn, but have seen very few people walk the walk professionally when it comes to influencing their own workplace to stop using it in some way. I have advised every company I have worked at against using external recruiters, and rarely has it been accepted (even though we always got a lot of candidates from the external recruiters who weren't a good fit with regards to either skills or eagerness).
Props to the article author for actually doing so, and I hope they will remember this and not use LinkedIn when the company they are cofounding has to recruit their N > 20th employee.