In BG1 and 2, I played a sorcerer. You know, they really need to get the sorcerer class out for BG3 soon. That might help peoples perceptions of spellcasters. The sorcerer differs from the wizard in that you get more spell slots but the tradeoff is you can't learn as much of a variety of spells.
You're thinking of 2e, 3e, and 3.5. The only way in 5e Sorcerers can get more spell slots, than the table allows per long rest, is by trading in Spell Points. Not a good trade once you hit 3rd level and gain Meta-Magics. All full casters, except the Warlock, have the same base spell slots. Wizards can recover some of these slots per long rest as well.
Sorcerers don't need to prepare their spells, and have all of their spells available. But they are very limited in spells known 1 + level. Wizards can prepare a number of spells equal to their level + Intelligence modifier. Clerics have the best prep list in the game, they prepare level + Wisdom modifier + Domain spells. But Sorcerers have Meta-Magics which make up for their deficiencies.
I don't particularly care how they limit long rests. They just need to. So far the best methods that I've read are either:
1. Story Timed Events, as I detailed in previous posts
2. Prerequisites, as Ive detailed in previous posts
3. Random encounters, as many have also suggested
4. Severely limit fast travel and make only certain areas rest zones
The problem with 1 is people don't want to feel limited or rushed. People are resisting it because they want to be able to spam long rest as much as they can without consequences.
The problem with 2 is if you really need to long rest in order to beat a boss, and you don't meet the requirements, oh well. You're out of luck.
The problem with 3 is that it is pointless unless you severely restrict fast travel. Otherwise, yoy can always annoyingly fast travel to camp and then long rest and then fast travel back. All this does is make you do more work for no reason.
The problem with 4 is that fast travel is nice and really cut down on senseless running through map locations you've already cleared. If you restrict fast travel, it just annoys players rather than prevents long resting. Instead of fast travel to a rest zone, now they have to manually run there. This was an annoying aspect, frankly, of the older games.
My favorite is 1. My second is 2. With 1, you can have more diverse gameplay with different endings and rewards based on how many long rest you use. 2 is more like Solasta, where I got the idea, and it could prove annoying if they do it wrong. I don't really care too much for 3 and 4.
I'm partial to # 2. Out of Short Rests, plus 1 food item per party member. I'm not opposed to random encounters, though I'm not sure how that is supposed to discourage long rests.