1e and 2e also had several times more spell slots. They were unreliable cannons with lots of ammo while 5e are highly reliable casters with a small magazine.
Earlier editions: 20th level caster in melee casts meteor swarm, fighter interrupts spell. Caster moves behind meat shields, casts meteor swarm, archer interrupts casting. Caster drinks potion of invis, moves behind cover and casts meteor swarm the next round. Repeats with Sunbursts and delayed blast fireballs over next six rounds as heroes try to find them, having all spells 6th and below left.
5e:20th level caster uses meteor swarm. If a counterspell caster is around with a reaction, roll dice to see if the spell goes off. Otherwise it goes off. Over n3xt six rounds launch Sunburst, Delayed Blast fireballs and upcast fireballs, using up all 6th- 8th spell slots.
5e + 1e disruption: 20th level caster in melee casts meteor swarm, fighter interrupts spell. Caster moves behind meat shields, casts 8th level sunburst , archer interrupts casting. Caster drinks potion of invis, moves behind cover and casts 7th level delayed blast fireball the next round. Over next six rounds exhausts all spells 5th and 6th level spells, down to just the 4ths and below.
Similar....but not the same.