Social democrats (e.g. Nordic model) are left of center, but aren't MLs or communists. Anarchists (e.g. Kropotkin) are left of center but aren't MLs or communists.

There's plenty of room between the center and Marxist Leninism.

I would say many labor politicians are centrist. Some democrats are center, some are center-left. Some are center-right.

Some members of Liberal parties are centrist.

The center has tons of parties in it.