There are a number of things which make judgements about teachers and discipline or sacking if needed difficult.
One is that parents are understandably very invested in their children, but don't see the full picture. This isn't the parents fault ...of course they don't know the full picture as they aren't there all day and don't necessarily know about lots of things going on outside the classroom that the teacher is or isn't doing and other demands from the school. Individual parents and groups of parents do make judgements about teachers and some make complaints. Some of these are justified and warranted and some aren't really....but especially when a group start jumping up and down, schools have to investigate of course. And some schools are better at spotting the differences between parental dislikes and things which make a poor teacher and throw which aren't. There are schools which lean over backwards to keep parents on side and are not supportive of staff.
Of course there are things which parents need to complain about....but it is all complicated by parents thinking they have the full story and know exactly what the teacher is and isn't doing.....but they don't.
Schools need to investigate complaints from parents or issues raised by children or other staff sensitively but objectively too. Sometimes someone gets a bad name with parents or children and it can be difficult then to be dispassionate in investigating and helping.
And what warrants dismissal or disciplinary action? For many parents it's a lack of obvious marking in ex books. But schools will,tell you that feedback needs to happen, but it's not just written feedback by staff but peer feedback, self feedback, verbal feedback by staff etc etc....it all becomes a bit more tricky then for parents to judge....quality isn't just the amount if red or green pen. And marking is just one element of teaching. There's lesson preparation if individual lessons, fitting them into the wider schemes of work which develop skills and content over a longer time period, there's tracking of progress, there's classroom control, there's explaining, there's making fun and interesting, there's developing test skills......most parents would be very hard pushed to comment accurately on an individual teachers strengths in each of these areas...but they all make up teaching.
Parents do get a sense from children about teachers. Sometimes the sense is that someone is not popular,msometimes it's that they don't have great control, sometimes it's that they don't explain clearly. Or all kinds of things.
Personally I'd simply say it doesn't help to decide or state 'X is a bad teacher ' but if you have concerns,more port the exact things you are concerned about. Then it has to be left to the school to investigate and decide if this particular thing is an issue or not and if it is part of a bigger problem or not.
In most jobs, people have to carry out many tasks. They might be better at some than others, but being weaker at one won't necessarily make them overall incompetent.....but this is the judgement many teachers seem to get from parents.
All of this isn't to say that there aren't useless people out there. There are some who simply don't work hard enough or efficiently enough or who don't think ahead enough to a manage the multifaceted thinking ahead which is needed to make it all work and get everything that needs to be planned, covered and recorded dealt with. Absolutely,me very child deserves teachers who can teach them effectively, even if they do have areas of strength and weakness.
Is it going to improve? Well teachers are under great scrutiny as mentioned above. They are observed and observed and their paperwork is looked at they have to give account for progress frequently....things don't stay hidden for lomg. And at the same time and because of both workload and scrutiny and pay issues and morale, huge numbers are leaving and they are massively struggling to recruit....so will the top quality people be coming into teaching? Probably not.
In my view the funding crisis will make standards in state schools decline to a point of such crisis that by the time the government decide to invest and act, it will take a generation to turn it around from a very low base for the industry.
How depressing.