In-combat spells are already garbage at high level play compared to non-spell-based classes. Too many things have spell resistance, damage/condition immunities, and legendary resistance. An extra action to cast a spell is only punitive in combat, which is the place that spells are already pretty bad.

If you're upset about high level spells, I have to assume you mean the out of combat ones. In which case, who cares how long it takes to cast?