We actually have gained a number of good things. I only know a good source in danish, which most likely wouldn't be of good use to you, but here's a great page available in english by a quick google:
www.myeu.uk
There's a reason that most europeans actually quite like the EU:
https://ec.europa.eu/commfrontoffice/publicopinion/archives/eb/eb49/eb49_report_en.pdf
Why? They earn way more than 13B$ long term, and makes them a corporate haven, which provides them with even more money, so it makes pretty good sense for them to be on Apples side.
Simple: Most people think that companies should pay their share of wealth to the societies they operate in, and not just channel them out of the country.
The average age of EU staff in 2018 was 48, which isn't really 'old slugs' by any means. And surprise, surprise, we do actually elect them.