That is misleading- the question isn't really about Extend spell... it's about any metamagic used by characters who mostly cast low-level spells. Would you claim that level 1 wizards shouldn't use any metamagic? Then why do they get that bonus feat?
The change makes applying metamagic to low-level spells more expensive than to high level spells, which obviously hurts characters who make big use of low-level spells. This includes:
Low level wizards. Mid level wizards.
Low level sorcerers. Mid level sorcerers.
Low level clerics. Mid level clerics. High level clerics.
Mid level paladins High level paladins.
Mid level rangers.
It's a joke to have to repeat this again: A paladin who takes Extend Spell IS focusing on combat.