It's not just that they are poor quality candidates/politicians. It's that they have won a golden ticket into the Scottish parliament and are earning so much more than they could in a "proper job". Most of them have never done anything other than politics and if they have, it's been public sector work, or working as assistants to other MPs. All that matters is unflinching loyalty to the cause and never questioning your boss, whether you actually are any good at your job doesn't matter. Like Angela Constance, Humza Yousless, John Swinney, Margaret Ferrier.
Then you have people like Ross Greer who has NEVER had a job of any sort as he went straight from school to uni and dropped out after 5 minutes to be a "politician". He's now being paid £75k as a MSP (our money, remember) he could never ever hope to earn that sort of money anywhere else. So they all protect each other.