Cap'n Kobold
Hero
Indeed. Saying that granting Extra Attack to a random Sorceror is fine, doesn't take into account when they take a Hexblade dip and cast Shadow Blade or Necrotic Shroud.
Likewise if you're allowing feats to grant even more attacks, they will play merry heck with Paladins for example, which are build on the assumption of only one extra attack and so receive per-attack damage bonuses.
Granting Rogues additional attacks is the least disruptive example, because their damage scaling will not improve significantly per attack.
The issue lies with instances where a class is designed under the assumption of no, or only a single extra attack and has powerful per-attack bonuses or spells.
Likewise if you're allowing feats to grant even more attacks, they will play merry heck with Paladins for example, which are build on the assumption of only one extra attack and so receive per-attack damage bonuses.
Granting Rogues additional attacks is the least disruptive example, because their damage scaling will not improve significantly per attack.
The issue lies with instances where a class is designed under the assumption of no, or only a single extra attack and has powerful per-attack bonuses or spells.