In general I agree with you, but it seems like WotC is pretty resolved to not go back to splat-fest - not by a long shot, so I don't see any legitimate reason to actually worry about this. I do like the options that have been released. I thought SCAG could have done without some of the fluff, but the content that was in there was good. One thing they haven't done yet is release a new class, which after more than 2 years is starting to stretch the definition of "slow".
As far as the title of this thread goes, I don't think it's a matter of where the lines are drawn - obviously everyone will have their own opinion on that. It's when some people who don't want any new content at all want to shut down any such conversations (extreme or not), and crying "splat" every time is a convenient way to accomplish this. Not that there isn't a time and place recall the pitfalls of previous editions, but when it becomes a "thought-police's baton"... not ok.