Largely true up to now, yes - but nothing has been finally decided yet. It's safe to predict that business confidence, inward investment etc will depend on the type of Brexit: if we stayed in the customs union the impact wouldn't be great, but if we pull out then there will probably be long-term damage, and if we crash out with no deal there is likely to be short-term damage as well.
Even if we leave on the best terms for us, there will still be a long-term corrosion across many aspects of our lives, such as being left out of EU organisations and research opportunities. And of course, we will have no say in future arrangements.
One wrinkle concerning staying in a different form of customs union - like Turkey - is that while it will provide us with easy access for our goods within the EU, it could put us at a disadvantage with other countries, because trade agreements between the EU and other countries would not cover us. That means that while other countries could import their goods to us (via any other EU country) we could not export our goods to them, except by paying their usual external customs duties.