I didn't play a lot of 3E, I am talking about 5E. Players regularly take 30-45 minutes to generate new characters and they know what they want before they go into it (meaning they have already actually done some of this work).
Choosing background, choosing origin feat, rolling abilities (or doing point buy), choosing skills, species abilities, languages, comparing that to what you get in your background, choosing weapon masteries, then adding a subclass and new abilities and feats level-by-level and potentially adding new classes. All that takes time and that is before you do any spells, and it is not even considering the backstory of the NPC.
It would be extremely difficult to build say a 5E 10th level Rogue and get all of that determined and written down in 5 minutes from scratch and I would like to see someone actually do that. If you are doing this in 5E I commend you, but most people can't do that. Now if you want to build a character that has a 20 Dexterity, 20 Charisma, 9d6 sneak attack, Cunning Strike, Assasinate, Evasion, Reliable Talent and Expertise in 4 skills .... I agree you could probably tackle that in about 5 minutes if you write fast, but that is not the same as a 10th level Rogue built according to the PHB rules.