In the UK we simply did not have the jet engines - We had the Spey & the Conway - was that it at that time?
The Trident ran out of steam and eventually needed 4 engines and 1-11 500 (was a nice plane) but the Spey could do no more for it...
And the very pretty but thirsty and noisy VC-10 was quite doomed by then
Thus the 727 737 and DC-9 swept along in...
The Yanks had the PW JT3D JT8D and pretty soon the JT9D - as did GE had the CF6 by 1971
We were watching RR lurch from almost failing to financial crisis' trying to get the RB-211 fixed and going which once we did OK by 1972 it was on the Tristar - but touch and go at the time