3 format workload is no joke. A heavy FC workload is not as damaging as constantly switching from T20 leagues to FC bowling and back.
That's why modern bowlers get injured a lot more.
You can see that in 2 specific examples - Shami and Hazlewood. When their T20 workloads started spiking around 2019-2020, their injury rate started increasing consistently.
Bishop has offered a theory as to why it happens. He said that video analysis revealed to the West Indies quicks of his time that their bowling actions were biomechanically different for both ODI's and Tests. They were trying to cramp batsmen for room in ODIs and their actions tended to change when they switched from Tests to ODIs.
It's even harder on bowlers now as they have to constantly look for variations in T20 cricket and then go play Test cricket with a consistent action to hit a line and length.
Contrasting stresses and strains probably lead to more injuries.
Also, many bowlers have in the past have admitted to cutting down on pace while playing county etc.
You can't do that in leagues where a lot more is at stake.
So, if Wasim and Waqar did choose to play a lot of league cricket , it's almost guaranteed their longevity would've taken a beating.