I wouldn't say training standards are poor, certainly not Driver training anyway (can't speak for other grades, although various threads on here suggest commercial training can be improved).
As for avoiding Serco/Abellio, again I'd rather be under them than First or Stagecoach. Granted Serco have taken on less than glamorous franchises that the larger groups seeking gold didn't fancy but as an employer they are quite good and not intent on ruling with an iron fist. Given the franchise terms Serco/Abellio took on with Merseyrail,Northern and now GA I don't think we've seen what they would do given the opportunity to renew a fleet or even refurbish interiors fully. Yes, they could be better, but they could also be a lot worse.