Centrism doesn't exist, they're all conservatives that don't like being called conservatives. The only thing they ever do is to give out the bare minimum of concessions to keep the status quo going.
That's true for American "centrists", but not for some European centrists. Centrists here are often either conservatives that are pretty left relatively to their party or social democrats that are pretty right relatively to their party, meeting somewhere in the middle.
Nope, France is unfortunately not breaking the circle, because the left did not win the election, they just have more MPs than the others, but not at all a strict majority. Now, Uninspiring "center" and right (and why not some far right) are trying to form an alliance to form a government...
You break the cycle by voting. It's all relative, you could have things cycling between "leftist" and "centrist" but leftist not voting means it cycles between "centrists" and the right-wing.
Are you forgetting to include a dishonest leftist that "solves" all the problems with policies that only increases them, or are you calling the leftists "centrists"?
It always makes me laugh a bit when people describe neolibs as leftists lol. Then I just feel dead inside at how common it's become for people to confuse centre left liberals for leftists (or even centre right in a lot of cases, especially the US)
Except the US(I don't know other countries politics) doesn't have any leftist politicians except maybe Bernie. If their first goal isn't social policies and their second goal isn't expanding personal liberties(civil rights, women's rights) then they are not a leftist.