Level 1 adventurers in 5e are not common farmers or common soldiers. There is an assumption that PCs, or individual with fully fleshed out design, are exceptional individuals through talent, experience, or both. If you look at the NPC stat blocks available, most of the closest equivalents to a PC class aren't as effective. A knight is sort of a lesser paladin and a berserker is sort of a lesser barbarian.
That said, notice that some of the people stuck on that nautaloid were, indeed, farmers, bakers, students, and the like. So even if level 1 in 5e wasn't beyond the average person, there are several commoners there that are on the ship, so it makes sense someone lower level would be there.
Also, it seems Gale's story is he used to be much stronger and was smashed down to lower level. Karlach seems to have a similar situation. As much as I don't miss Level Drain as a mechanic....at all....the backstory of "I once was stronger than I am now" works perfectly well as an intro to a new campaign and character.
Having a video game start from higher level is tempting but I don't think it would be the best option in the long run. Among other things, some people don't like to just jump to high level and design the higher level character. They like to tweak the build here and there as they level to make sure there are no holes.
I would say that this "drop them in the deep end" wouldn't be a great tabletop design but Out of the Abyss exists...so there's that.
