Definitely not the case for Paddington - Devon / Cornwall as mentioned by Hopwood several time on LinkedIn.It's noticeable in the figures that you quoted earlier that it's GWR's longer-distance routes that are performing worst.
My experience tells me there has been a significant increase in business users visiting London for 1/2 nights and travelling in the shoulder peak, midweek the car parks at the likes of Exeter St Davids are full. This combined with lower usage on the Swindon - London corridor reflects the move to hybrid working and business people being more willing to travel further when visiting London in exchange for a better work / life balance.