Switzerland has a thriving sector of R&D companies, in various fields including biomedical (working in such a company myself, moved from an EU country), and various other fields of engineering. It is the backbone of the economy, much more today than e.g. 20 years ago when the financial sector was much more dominant than today.
While I agree that brexit probably was a bad idea, and I would have hoped the UK to use its weight inside the EU to improve it, instead of leave it causing damage to everyone, I am not so sure about Switzerland and how wise it would be to join.
The EU does have some serious problems that should be fixed first.
Also it cannot happen, since at least 80% are against EU membership, and Switzerland is a real democracy with binding referenda at national level.
They are against (left to right, not only the right), because there is much to lose.
The economy is still doing much better than e.g. over the border in southern Germany.
The minimum wage is high. The EU demands (even now, just for the trade agreement) free access and movement of workers, with lax controls against wage dumping. This is one of the main reasons that the left are also against joining the EU.
It would lead to poverty amongst less educated parts of the population, and to social unrest.
This is an egalitarian and informal society, typical for a small country with high degree of autonomy, joining the EU would destroy that.