True. but when a debuff works, it typically hurts an enemy much more than a buff helps your allys. The real downside of debuffing is legendary resistance but that comes up fairly rarely and it really doesn't turn up until higher levels.
Keep in mind there are plenty of group debuffs like slow or hypnotic pattern and many debuffs scale up in number of targets so you can usually target all the enemies or at least all the important enemies with a debuff. Buffing only typically affects 1 ally or 2 at most with twin spell.
Spells that only affect 1 target tend to be powerful while scaling to multiple targets requires waiting 2 more levels and spending a higher level slot.
Keep in mind that slow and hypnotic pattern are also sorc options. The difference is that quicken (or another meta) can be applied for more effectiveness in the same turn.
I stand by my comment, however. DC's are still low enough when those spells come online to carry risk even against weak saves. Bonuses, immunities, possible advantage, etc increase that risk.
Take some of both. Any caster can do that.