That may seem to be the case because stat blocks take up so much space, but every published adventure I've ever read has had plenty of non-combat content. I'm sure there are groups who ignore all that, but that doesn't mean it's not there.
I assure you, 5e was not designed with the intent that combat should be more important than exploration or social interaction. You could argue that that was true for 4e, certainly, but during every step of the 5e design process, Mearls et al made it very clear that all three pillars were extremely important to them, and they didn't want any one of them to outshine the others.
I'm not saying your way of playing is wrong, however; if you do value combat above all else, then I will completely agree that the rogue class is probably not right for you. But you cannot claim this is a design flaw, because to do so would mean you are ignoring two-thirds of the game the designers set out to create.
It is unfortunately the way we play. We have a couple of players whose eyes start to glaze over when combat doesn't occur quite often. When major roleplay encounters are occurring or scouting or out of combat stuff, it is usually resolved within 10 or 20 minutes. If it is not, players start to disengage from the game finding other things to occupy their time.
I would bet money this is not something that occurs only at my table. The game is made to advanced based on combat encounters with occasional roleplay and out of combat scenarios that add xp. The majority of a party is made up of classes that have very little to do out of combat or in roleplay situations due to the focus nature of each class. A DM can't engage with one player for too long a period of time without causing the others to grow bored. Combat is the one event that involves all present. That is why most DMs focus on it heavily to keep the game engaging.
Not to say anyone should or has to play this way, just that the majority most likely do. This talk of three legs should be more of a graph with a roleplaying and out of combat scenarios making up a very small percentage of the graph and combat making up a very large percentage for the majority of adventurers.