Parliament will hold hearings over the next month to scrutinise the Commissioner Designates and will then hold a vote to approve the entire college of Commissioners.
And this process has, actually, resulted in unsuitable candidates being either replaced entirely or portfolios being redistributed in the past (including the last time around in 2014).
Parliament can also sack the Commission at any time if it so desires. That last happened to the Santer Commission in 1999.
This is more democratic legitimation than most ministers in most state governments have, where ministers are often appointed by the head of government without confirmation. (The EU commission is similar to a government and commissioners are similar to ministers in their role)
Look at how the head of the Commission was chosen. Remember, the entire Commission reports to one person. The sub-Commissioners are theoretically (by treaty) nominated by each country but in practice the head of the Commission controls all the appointments. As Jean-Claude Juncker openly admitted, if he didn't like an appointment he'd simply reject it. He isn't meant to have this power, but claims he does and I believe him. The EU is full of things like that.
So the entire Commission reports to von der Leyen. How did this woman get the job? Nobody can tell you. The decision was made in secret. No minutes of those meetings were published. No leader justified the decision. If there was a vote at all, nobody can see which countries voted for her or why. It just ... happened. Literally the only statement I've seen about what criteria was used was, "it'd be great if this time we had a woman", which came from some EU President (there are several and I forgot which one). So I guess that must have been why she got the job.
Theoretically the Parliament can pick the head of the Commission. When they picked Juncker last time around, the EU went along with it and liked to claim it was getting more democratic as a result. But this time, when MEPs committed the hopelessly un-woke crime of nominating a man, their nomination was ignored.
In true Soviet style, the EU Parliament got a vote ... but because MEPs didn't want the terminally incompetent von der Leyen, it had to be fixed. No problem - MEPs were presented with a vote in which von der Leyen was the only candidate they could vote for!
Despite her being literally the only candidate on the voting paper, so many abstained from this farce she still got the lowest number of votes in history.
So that's the EU. There are votes, there are politicians, there's a Parliament. Just that none of them matter.
But it gets worse: Ursula v.d. Leyen has a history of trying to implement countrywide internet cencorship in Germany (and is since called "Zensursula"). And could only be stopped because of a gigantic rise of the Pirate Party (now defunct) to levels that became dangerous to the establishment.
The Spitzenkandidat system isn't law per se - it's a (very new) convention mostly being pushed by the European Parliament. The European Council (that is, the presidents, prime ministers and chancellors of each EU country) has always had to give or withhold an endorsement to whoever the European Parliament proposed to lead the European Commission.