I'm afraid I disagree entirely. If your business is aggregating data in order to sell more effective advertising then you are walking a line and need a lawyer. If your business is selling widgets and you collect personal details in order to complete orders then you are just going to have to write some documentation.
I can tell you as someone who is working in an old school retailer/wholesaler we are not, and neither is anyone we are talking to through various trade bodies, employing lawyers to do GDPR.
Actually, you can keep order data as it has to do with VAT law but you have to keep it in line with GDPR... So it not just writing some documentation, rather making sure your data is secured with up to date and taking into account state of the art technologies etc...
Lawyers can't help you with ambiguous laws very much as it takes precedents to make sure what the words mean.
Again, part of the problem is that it's not clear what does and doesn't constitute a violation.