Unfortunately its a franchise thats suffered from lack of investment for decades, main issues currently is a lack of units as discussed, plus youve got the 175s which due to lack of gangways are hard to operate on a lot of routes in multiple because of the lack of gangways. Stations with short platforms of which there are many, means locking out the rear unit for those stations and faffing around rounding passengers up from the rear unit for the next station etc before locking it out - or the whole journey (which defeats the object).
Hopefully with the 197s and their gangways, it should be possible to run more longer trains with their selective door system, and passengers can move through the gangway into the correct coach. Unfortunately these things take time but hopefully after years of neglect, things should improve.