Until you’re senior enough that most of your job is communication, then remote becomes difficult again.
WFH now and maintaining Work/Life balance is really difficult when most of your time is spent sending emails, reviewing code and proposals and answering questions in a global company.
Writing code at night happened occasionally before, but it required leaving my family and pulling out my laptop so it had to be for good reason. Helping an overseas team out over Slack with something at 11 pm can be done from my phone, “it’ll just take 5 minutes”.
In terms of pure work productivity, I disagree. Emailing, reviewing code, and reviewing and writing proposals are all activities that are best done in a low distraction environment, which the modern open office is not. Dealing with questions has a bit more overhead on both the asker and the answerer, but I don't think it's so much that email and Slack don't mostly cover it. For those occasional instances where written communication doesn't cut it, video chat is an acceptable substitute in exchange for the benefits in other areas.
Even for whiteboard discussions, you can buy a literal whiteboard for your work area, hold the meeting over video call, and exchange photos afterward. It's not quite as low friction as walking up to a whiteboard in the office with a coworker, but, at least you know the damn markers will work.
Maintaining WLB is something one needs to be attentive to. Having a dedicated work area as well as maintaining specific work hours (and sticking to them) are key. Other than that, I don't think maintaining WLB at home has to be any tougher than at the office. Kids present special issues, but, if you're a non-WFHer, you already have provisions for the kids during work hours, anyway.