I don't have an issue with BG3 having Origin Characters (and i did enjoy DA:O origins as well) as long as they can be customized somewhat, but related to custom chars (which i also like to play with) story and personality I agree and Larian could experiment a bit more by giving us more options to alter their backgrounds and make them feel a little bit more personal.
There are multiple ways devs can alter char background in an RPG, for example a character can reveal more deep details about her/his background during dialogues with companions and other npcs who are asking about her/his past. For example if she/he is a Folk Hero the character can describe how he/she became a Folk Hero via different dialogue options. This choice can be memorized by the game and used for an npc reaction later in the game even (Hey its you who did this and that). Let the player decide on the go and roleplay. But this is just one way.
There can be origin templates as others already mentioned which if cleverly designed basically are giving you origin characters but with no restriction on race, appearance, personality and some flexibility on classes. Personality can be altered by Personality Tags again if cleverly done.
I also like what the Realms Beyond (the available combat demo) does with your history, it alters the predefined origin text you are able to choose from (scoundrel, farmhand, craftsman) by how you distributed stats and skills, which is really cool. Basically the game tells you how your characters abilities served him/her and evolved while reaching her/his early life goals (defined by the chosen origin story). For example Artist background with only medium Dexterity reflected: Levi tried his hand at the traditional arts of Pyrrhenia: pottery, sculpture and painting. Levi's works were mediocre, but he showed promise and earned enough denarii to make a decent living. As you alter your stats, its fascinating to see how your pre-story changes, i think its really clever, feels personal and not too much resource it needed to implement (a lot of planning though).
Overall I just hope Larian also can add more cool flavour to custom backgrounds.