Really????
So you’ve obviously missed the 9 car 800’s that have been knocking around in the Cotswolds. I’ve been on a mid morning 9 car train Paddington bound and there was about 5 of us in the carriage. One of my regular trains is 1W29, a pretty solid 800(5) turn and that is never rammed.
I’ve been on one recently that was pretty cosy with vestibules full but that was a 5 vice 9 and the vast majority of the vestibule dwellers got on at Hanborough and piled out at Oxford!
Also near in mind that the IETs are replacing HST, 180 & Turbos on the Cotswolds.
Where’s @jimm ? A daily traveller on the Cotswolds.
Away for a few days...

Unimpressed with GWR's removal of 8 carriage HSTs in favour of 5 carriage IETs on the Cotswold line.
Even during off-peak weekday services there is standing room only.
Departing PAD it's often fully loaded in the weekday afternoons (not peak services). This is where the IET has replaced what used to be an HST so a drop in capacity.
Which service(s) are you talking about? 'It' isn't exactly much of a clue, is it?