Honestly, at my last company, in my first team we reserved the fridays afternoons for demo and short formations (the most complex, that also resonated the most with me, explained how and why the network architecture was made, while some were as basic as explaining how to make good PR).

It was way more productive than with my second team where we used one hour every two week for the retro. In big company, the time you actually spend on understanding how everything work is never really lost.