If HLTB is any indication, than MUCH slower, but I also think most people are, because HLTB is probably mostly frequented by people who try to get through games quickly, or even speed run games. I think if you looked at true averages (ie. most people never even come close to beating video games), I'm probably average, or maybe even a little above average....but I don't know what those averages really are because of my first sentence.
I've seen a few posts like this in this thread and I think its just different perspectives, because for me I look at HLTB after I finish a game and wonder what people were doing to take so long. People are just different I guess. I don't recall ever finishing a game slower than the HLTB overall "all playstyles" average playtime, and I check it quite often.
Some examples recently:
TLOU2 - HLTB 28h, me 20h
Cyberpunk - HLTB 57h, me 35h
Immortals - HLTB 39h, me 26h
Demon's Souls - HLTB 33h , me 19h
Rise of the Tomb Raider - HLTB 25h, me 16h
So yeah, probably on average about 30% faster than most people.
I don't think I rush or try to speedrun, I could certainly have done all of those a lot faster if I wanted to. I just don't linger or dwell on things, I'm not one to stop and look at environments or models because they're pretty, I don't enjoy stopping to a crawl to look through every nook and cranny of a level, I just have one decent look around to see if anything stands out. I think it does help that I'm probably better than the average person at most games and I prefer to keep it on normal difficulty and kick ass than trying to artificially challenge myself with a high difficulty, so I tend to fly through most games without failing much.
Like with TLOU2, I don't think I missed anything important in that game and I never ran out of supplies or ammo, sure I didn't go for 100% but I got about half of the collectibles. I even felt like I was being slower than normal and really taking my time with that game. In Cyberpunk I did every important side quest the game presented to me before I finished it.
I guess it also depends if you go for trophies and collectibles the first time round and count that, because I never do. I just play through a game naturally, usually trying to complete most side content I've come across if I am enjoying playing the game. Then if I really love a game and still want to play more after seeing the credits, I go back and try to 100%.