No Class System is a Good System
Every RPG class system is bad, but before I tell you what you should want, let me tell you about you. Or rather, let me say whom I want to speak with.
I'm not writing for people who enjoy class systems, so much as for people who want to sit above it all, with an ineffable air of enlightenment, saying 'everything is preference, truth is a lie'. I'm here to 'eff' their air, and bring them back down into the muck. People may prefer a poke in the eye with a sharp stick, but since we make reality-based judgements about washing-machines, the health of eyeballs, and quality of food, we can definitely make statements about game mechanics.
So if that's you, I want to hand you some Empiricism-muck, i.e. the kind of concoction which looks like Maths, but doesn't work until you plug some standard intuitions in.
The Necessity of Skills
We're long past the days of old D&D, when characters could get away with having 'weapon proficiencies', and bugger-all else. Nowadays, class means skills, which naturally entails a big list, and a point-buy system of some kind.
Whether the book presents these skills as abstract points, or previous professions makes no mechanical difference.
Having making a D&D fighter vs a rogue means a plain choice - you go the path of the fighter and take bigger pluses to hitting things, or you take more pluses to the many not-hitting-things abilities on the character sheet.
The Alternative
The other path beckons - clear as daylight and burning the eyes of everyone watching shadow-puppets of clerics and paladins dance across the cavern walls - you could just allow people to buy a +1 bonus to hitting-things in exchange for three or four loads of +1's to not-hitting-things.
And clearly, the same could be done with magic. What is a ranger, but a character who has bought a few levels in hitting things, with some pluses to sneak-by-things, and (much later) some spell-casting? What is a paladin, but hitting-things and spell-casting?
(And while we're both here, why on earth does D&D insist on having so many methods of healing? 'Lay on Hands', plus 'Little Heal', plus 'Medium Heal', plus 'Drink-Heal'? You really need four separate systems to make HP go back up?)
Tables First
These extra steps to build a class system out of individual abilities don't save time. They don't allow anyone more choices, but also can't help with choice paralysis when they force you into making choices all the same.
The primary thing they do, is front-load the book with tables upon tables, which people have to reference by making a character. If you think through all the RPGs you've ever played or read, you can probably remember how to build a character in most of them.
However, the only class system people can occasionally memorize is D&D, and its derivatives, because it's so ubiquitous, and has stolen so much of people's time. Take any other class system - with tables and descriptions, each showing pluses here and feats there - and barely a handful of people in the world would be able to tell you how to build a character from memory. Even the creators of these games probably don't recall which steps to take where.
A Class by Any Other Name
Whenever someone speaks about the real benefits of a class system, they end up describing something good in an RPG, which has nothing to do with class systems.
Classes let people know who they are - stereotypes are sometimes useful.
Yes - like some kind of less-serious but more-pretentious Astrology chart, RPGs employ stereotypes. But there's still no need for a class system. You could just write 'rogue', 'wizard', or 'warrior' as a concept at the top of the page, and go from there.
You could even provide a list of suggested starting skills. In fact, if we rebuilt D&D without a class system, we could still begin with identical level 1 warriors and level 1 thieves, at the start of the book. These would not require any tables, they would just be 'suggested characters', and players could adjust a skill-point here or there, as they pleased.
Classes give people a role in the party.
Again, this is true, but doesn't require a class system. A Vampire: The Masquerade game could employ one vampire who's needed to 'be the muscle', and another who 'has all the contacts'.
And if D&D desperately needs someone with healing magic, that shouldn't speak well of its class system, it should speak badly about the entire game.
Locked In
And of course, if we compare a classy-thief, and classy-fighter to their messier, point-buy counterparts, an unfortunate truth arises: they were identical until their stats increased, at which point the classy D&D characters had to pull out those tables, and find out where they had to spend their points. Meanwhile, their counterparts could spend their points just wherever they liked.
Being classless means spending your own XP. And when that classless fighter and thief can spend their own XP, either one could move into being more of a 'ranger' archetype, or even a late-blooming spell-caster.
Those with class, however, must remain where they are, as the system locks them into their role, even if they made that decision two actual years ago. Those with class are not only locked in, they are locked into one of three, or twelve, or whatever-many-archetypes. If any of them wants to break the mould and play 'a resourceful hatter', or 'a prophet-warrior, like Joan of Arc', they may have to stop and invent an entire class, rather than just spend the points where they want them.
The Madness of Multiclassing
At this point, people will naturally bring up multiclassing. If the thief wants to move into wilderness travel, and become more of a ranger-archetype, they can just 'take a few levels of Ranger'.
To misquote Jeremy Bentham;
Class systems are nonsense. Multiclassing is nonsense upon stilts.
Won't Someone Think of the NPCs?
Beyond the madness of multiclassing rests 'NPC classes', where someone can become 'a level 5 seamstress', or 'a level 8 blacksmith'. And if all NPCs are effectively 'level-0', this begs a few questions from all the well-studied wizards anyone might meet.
"How many dragons have you killed? Are there any monsters you haven't yet seen? Where is your rope?"
These may seem like odd questions to ask of someone who spends their days studying arcane languages in order to cast spells, but apparently all spell-casters enjoy a 50/50 diet of contemplative study and spelunking. Because if mages can master the five elements and cast mighty spells by just sitting and studying, why wouldn't the PCs do that?