First, we were actually still using the M101A1 in the 80's. It's a nice little gun that can crank out 10 rounds/minute with a good crew.
Second, you can have different guns for different missions. Even when the M101's (usually just called "05's") were still a primary gun for direct support units, we had 155mm and 8 inch artillery for longer range/counter-battery fire. Those larger calibers tended not to be as good for direct infantry support as their rate of fire was slower, and they took longer to emplace/CSMO. The '05's were great for shooting and scooting in a direct support role, and the larger stuff was used for longer range/counter-battery fire.
Also worth noting that the light '05's can be used more effectively when there is mud/bad weather/bad roads, etc.. Much less likely to get stuck, more maneuverable etc..
Anyway, while using 05's certainly is not ideal in 2022, the criticism that they are outranged by some Russian artillery misses the point that they are not used for artillery v. artillery duels anyway. We have HIMAR's, M777, and other stuff for that.
>>> “Even when the M101’s (usually just called “05’s”) were still a primary gun for direct support units, we had 155mm and 8 inch artillery for longer range/counter-battery fire. Those larger calibers tended not to be as good for direct infantry support...” <<<
WAY different eras and missions.
From Vietnam to Afghanistan, USA Arty was NEVER in “artillery battles.” Not even in Khe Sahn, but that was probably the closest. [Until we cratered their firing positions with B-52s, with 100% air superiority from piston pushers to the stratosphere.]
Outside of (maybe) Khe Sahn, American arty has been firing from basically safe semi-immobile dug-in fire-bases in support of random USA troops on the ground. From 1966 in VN to 2000 in A-stan. You have to go back to Korea to have actual “artillery battles” on even terms. So basically, we have ZERO experience at massed arty in living memory.
In the Donbass, it’s much more like WW1 or WW2: massed arty, mano a mano. If our 155s outrange your 105s, you are dead. We find and hit you before you even sneak into range.
Data point often now mentioned: The M-777s and other NATO 155s are asked to fire more rounds PER DAY in the Donbass, than in Afghanistan IN A MONTH.
What is great for firing random precision rounds at goat-humpers near a squad of American troops in A-stan, is NOT great for firing 100s of rounds per day, every day, in the Donbass, when the enemy is firing back with fast accurate counter-battery.