Normally I would think a drop in replacement would mean I could switch to it and do everything the same as I was doing it. But my guess is that if I did this drop in replacement that little to none of the web activities I partake in would work anymore. So maybe my thoughts aren't quite what is meant.
I'm not sure what this means.
> it's drop-in from the perspective of the user
From my perspective as a user, if after doing the drop in replacement, I can't use my bank's web site or browse Hacker News the same way, or watch TV on Hulu, it's not a drop in replacement because what I did before no longer works. It's not clear to me if this is the case with Freenet.