It's true that the classes don't add much, and they aren't well balanced either. The majority of experienced players pick Hunter or, if they're bored of Hunter or thinking more about the late game, Clockmaker, in order to get the increased movement speed. Personally, I just feel bad if I'm playing the slow classes. Some argue for Malefactor's ability to obtain more gears by selling cracked vessels to traders, but I personally feel like it's easy enough to get enough gears for whatever you want without it.
If classes were removed from Vintage Story, I wouldn't feel bad about it. If you wanted to roleplay as having a certain background, the 6 available options make for a very limited set to choose from and aren't particularly interesting. If you wanted gameplay customizations, you can't really beat movement speed since it can compensate for everything else.
If anything, I don't understand why Vintage Story even needs to have classes. If you're playing with friends and class-specific recipes are enabled, then its little more than an inconvenience to whoever volunteers to pick Tailor to make everybody else a tailored gambeson, and a lot of people who play solo already play with the class-specific recipes disabled and then make the gambeson themself (or even obtain a couple pieces of tailored gambeson by other means).
The way that you personally choose to play Vintage Story says a lot more about who your character is and what they do than whether you clicked "Blackguard" or "Commoner" at character creation, and as far as I'm concerned, that's fine.
