There are some valuable elements to the paper.
It's a critique of the way the course materials are written, rather than of scientific content.
I do believe (based I suppose on experience) that groups who have previously been led to believe they are bad at something are prone to drop out if the course material is presented as difficult and the teaching style unforgiving of any weaknesses. So people from working class backgrounds, those with no family experience of HE. But in Science that would also apply to women, whose confidence will have previously undermined.
So if language is used which suggests there's going to be no time to go over a concept if you don't get it (because you should already know it) or that there will be little opportunity to expand ideas from the individual student's pre-existing knowledge base, then the course will be seen as more difficult with a higher likelihood of failure.
It is possible to teach a great deal of Science without using that teaching style. Where the paper falls down is that it doesn't recognise that some of those problems are going to apply more due to the subject area. Geology and Ecology, given as examples in this, are often gateway subjects for bringing people who lack confidence in Science back into STEM. That's because those subject areas allow someone who enjoys 'rational' thought but has knowledge or confidence gaps to get up and running pretty quickly. It's pretty easy to teach Ecology and allow someone to draw on already happening to individually know a lot about Mozambique or coal mines or whatever to build up an essay or project around that, picking up core elements of Ecology as they go along. You can't really do that with Algebra. Students really do need to know the previous steps in getting to that particular level in Maths. You can't just enjoy rational stuff so jump in without any Maths background.
But in general much of the language and teaching style that makes those courses the paper discusses appear difficult can be altered, as the writer recommends.
And those problems can happen on any course. For example, I was taught post modernism (and related theories) by someone who would take examples from what might be called a canon of Western civilisation, and then apply the theories to them. And then when people without a private school education asked what all this Corinthian stuff was (or whatever), the lecturer would be condescending, make us feel ignorant and so on. And I did feel ignorant and connected that to being from a comprehensive school, unwelcome, that post modernism was too difficult etc. All of that was unnecessary because the whole course could have been based on what we individually did know, and work post modernism around that.