Depending on which country, there still are mechanisms in place to fire people for what's called "culpable reasons" where I live, but there's a mandated layoff period (15 days here) after being fired to leaving the company. You get paid a certain fraction of what you'd otherwise be paid during that period and so on.
So yes, they can fire you if you (maliciously) screw up, but it's not like they just escort you out of the building on the spot.
Egregious cases can lead to immediate dismissal, you also don't have to let anyone continue working even if you still pay them if they are on the notice period (the notice period is for both sides, honestly - for employer to have chance to find/train replacement, and for let gone employee to find new work).
There's a bunch of cases that can lead to immediate dismissal though in most EU countries, starting with illegal activity, some things that are borderline (disallowed in law even if sometimes tolerated by employer - for example being drunk on the job or otherwise under influence by ones own action, not accident), or explicit action against the company.
So yes, they can fire you if you (maliciously) screw up, but it's not like they just escort you out of the building on the spot.