Some inaccuracies and unfair overgeneralisations in your post.
Majority of drivers I've encountered whether it be First, Stagecoach, Citybus or McGills (including Arriva before that) are very professional and very good at their jobs who do well to cope with the pressures of early starts, long shifts, poor weather, heavy congestion, rude and obnoxious passengers, inconsiderate road users etc. There are always a few that let the side down but you'll get that in any industry.
You're aren't comparing apples with apples when you use Lothian as an example as they are very well funded and are able to afford to run their business in a way that the big groups can't. Also, Edinburgh hasn't the suffered the same levels of depopulation (especially around the inner city) and deindustrialisation over a number of years like Glasgow has and many bus passengers have been lost as a result.
Nobody knows what the future holds but it seems to me that First are making a better effort under their new Scottish MD than previous leadership. No bus operator is perfect but I would say in Scotland only Lothian (for their presentation and clear information) and Stagecoach Fife Scottish (excellent long distance routes) are better than First Glasgow who at least offer good value with their monthly and annual tickets which Lothian don't.
The thing is that you won't get anything other than inaccuracies and overgeneralisations. This is a person who saved various First critical social media posts and recycled them, or thinks that Andrew Jarvis isn't a proper bus man despite working for his father's own independent bus company and then for Stagecoach before joining First.
We all know that First have got a backlog of issues and many of them of their own making. This has been covered
ad infinitum - whether it be a lack of consistent investment in UK Bus in new vehicles, having to accommodate ex London kit in the provinces, or when the money dried up, both a focus on profit margins that were unsustainable. Clearly, Mr Jarvis has now managed to get new vehicle investment and it doesn't matter if the LEZ is the reason - it doesn't reduce the numbers required nor get away from the money being spent. Similarly, he has clearly looked at how to improve midlife fleet. I look at my local First fleet and there are still too many old vehicles running in Bristol/Bath with some very tired looking Barbie liveried Eclipses. However, they have got a lot right under the current regime and it looks like a similar pattern of new buses, refurbs, and improved branding is being rolled out in Scotland.
Being brutally honest, compare most fleets with Lothian and you'll be disappointed, and for the reasons mentioned - it really isn't a true comparison. It's like complaining that all the women in the pub on the works' night out aren't Rita Ora and so retreating into your bedroom for a night of bitterness, self abuse and self loathing, when failing to recognise that the girl from accounts has actually lost a dress size and done her hair
I'd add a little note here.... my theory (and it's just that) is the lack of a Glasgow specific livery is that you need something relatively neutral in order to make the route branding (on those routes so treated and that will be in the future) be more prominent.