I used to work for a cloud provider that helped bootstrap business projects, research and start-ups, first in france then in the later years, all over europe.
Do you know how long it took to start a service company in France in 2018? Half a day. And the government own service that help a lot with online identity and paper filling wasn't even online yet, i'm pretty sure that if i want to start a limited company, and make this company employ myself as a freelancer/self-employed (don't know the exact translation), i'd be able to do it in a day.
To steal from other EU members is no competition it's just unethical. Small countries can live just by cashing a small part of the money that is rightly owned by countries with more population. That needs to be fixed.
Also obviously the EU can put in place any kind of controls it deems necessary on the common market. It’s sovereign in this matter after all and tax dumping is mostly helping foreign-based multinational corporations.