I say it's a bad thing. For both, Europe and the UK.
In my opinion, it shows that the British should never have joined the EU. At least the older generations never had the true EU-spirit. Looks quite a bit different among the generation of my girlfriend. She comes from a conservative British family, but her parents are pro-EU, and thus voted pro-stay in 2016. However, just for quite pragmatic reasons. They are politically literated enough to see that GB has more benefits from the EU-membership as the average Briton seems to see it.
But on the other hand, many continental Europeans have lost this EU spirit too.
The reasons for this is upmost the enormously increased bureaucracy and the associated regulatory rage within the EU administration.
And even more blame in case of this misery goes to the political decision-makers of each member states. Especially to those of the dominant member states. Also because they forced it, that many states could become member of the EU in the last 20 years. In my opinion, the EU has grown to fast. There was no time for development to reach a certain stable politcal and social level longterms.
Also, because they have never really discussed what it means to be a member of a community like the EU with the citizens of their countries or even forced a proper discussion among those citizens.
It means that each state inevitably gives up some of its own sovereignty to a union like the EU. If this had ever been propagated before joining the EU, no citizen would have agreed. And that's not a GB-specific peculiarity. That pretty much applies to every EU member state.
What Brexit means for the future EU can't be foreseen. GB existed before joining the EU and imo will do so after Brexit. But as my grirlfriend says, mostly old people voted pro-exit, and her generation has to pay for it.
But her generation is also free to re-apply for a EU membership if they eventually rule GB someday and they still consider being in the EU is still good thing. Hopeully they also won't then make the same failure as the old once in 2016 did.