Introverts can find working at home too isolating as well. I'm only mildly introverted so I was OK for a while, but then I started missing being around people even if not interacting on the project.
I think you have to be careful of your generalizations there. For instance, I'm not "mildly introverted" as you put it. Rather I'm completely off-the-fucking-MB-charts introverted. Because I don't rank high enough to have my own office at work, I'm inevitably stuck in a soul-sucking/energy-depleting cubicle environment. Or even worse: an open office.
Thankfully I've been 100% WFH since June of 2019. And I'm thriving! I've never been happier or more productive at work.
Ultimately, I think the best overall solution is as others have suggested: flexibility. For those hyper-introverted: let them WFH permanently. For others, a sliding scale as they (not the employer!) need for their own sanity and productivity.
I do believe that by the time we get to 2021, the likes of GOOG and FB will re-visit their "WFH until 2021" statement. They're going to check the general productivity levels of their employees, and likely extend that to "permanent". The next step: start shrinking office holdings significantly. No company wants to be in the real estate business if they avoid it. Specially in Silly Valley! The cost savings from taxes, insurance, and other OpEx could be huge.