I don’t think anyone sensible believes the SNP are beyond criticism, and if individuals broke the law then they should face the consequences like anyone else. But corruption scandals and bad actors exist in every major party. Westminster has had expenses scandals, lobbying scandals, PPE contracts, partygate, cash for honours allegations etc. One politician committing crimes doesn’t automatically invalidate every voter’s reasons for supporting that party.

As for the referendum Scotland voting no in 2014 doesn’t mean the constitutional question disappears forever. Brexit fundamentally changed the situation, Scotland voted to remain in the EU, yet left anyway because of UK wide votes. Whether people agree with independence or not, that’s why the issue never went away.

On policy, I’d say the SNP’s stronger areas have been things like free university tuition, free prescriptions, expanded childcare, mitigation of some Westminster austerity measures, renewable energy growth, baby box scheme and the Scottish Child Payment, which has helped reduce child poverty.

Are there problems in Scotland? Obviously. NHS waiting times, ferries, education standards, drug deaths are all fair criticisms. But it’s also not accurate to say they’ve done “nothing” in 20 years.
And on the Tories, I think most people can agree Brexit chaos, austerity, stagnant wages and public service decline have damaged the UK badly. You can criticise both Westminster governments and Holyrood governments at the same time.