Its true that Englands attack kept changing but it was never bad. For three of the four Tests they had a very good pace attack
1st Test : Snow, Old, Hendrick
2nd : Snow and Old (Because they brought in an extra specialist spinner in Pocock)
4th : Snow, Willis and Ward.
They had a good spin attack in every game with Underwood playing all five, Pockock two and Miler one.
As for the third Test centuries, the century in the first inings by Greenidge is considered one of the finest innings of that decade.
It was not just scored out of 211, look at what the others did
- Fredricks : 0
- Richards : 4
- K'charan : 0
- C Lloyd : 2
- D Murray : 1
Selvey (replacement for Old or Snow, had a fabulous spell and England were 26 for 4. But for the partnership between Greenidge (134) and King (32) West Indies would have been routed. The other 9 batsmen scored just 32 runs between them.
It was this innings of Greenidge followed by Holdings 5 for 17 which with Roberts and Daniell bundled England out for just 71 that demoralised England so much that they were so lost in the West Indian second innings, not the weakness of their attack.
I think to run down Greenidge's centuries (particularly the first innings one) is unbelievably unfair.