Maxperson
Morkus from Orkus
There are multiple issues that result in D&D being misperceived as combat focused.I see one problem with this claim in the larger context. You speculate that long winded combat is the reason D&D feel combat focused. However really long winded combat was introduced by WotC, while I would say TSR era D&D had an even stronger reputation for being combat focused back in the day, than I experience 5ed's reputation.
I think you really need to look at the larger culture. When I am running home made campaigns in D&D there are usually many sessions between each combat (and these campaigns are mostly formed and driven by player input). If I am running a prewritten adventure, I can expect at least 1 combat per session. That include enworlds excelent War of the burning sky, that is the least combat focused adventure path I have seen if run mostly as written.
1) As you note, back in the day 1e was much more combat focused. Even exploration was usually just to find treasure which was generally guarded by monsters.
2) This is one that I see most. RULES!!! There are many more combat rules(the combat section is by far the largest) in the game than the other pillars have. What they are ignoring is that combat by necessity needs many more rules in order to function well. I don't need all of the initiative, combat facing, OA, movement, etc. rules for the other pillars.
3) XP. Most(and often all) XP is awarded via combat. The game has moved away from that somewhat in recent editions, but the lion's share still comes from combat.
There may be other reasons, but those are the ones I can recall now. What the people arguing combat focus are missing is that in the vast majority of games, most of the playtime is spent in the exploration and social pillars. If combat is a minority of the time, the game is not focused on combat.
The change in focus from combat oriented 1e to the modern outlook on D&D means that those who still play 1e generally also spend more time roleplaying and exploring than they used to.