An actual criticism of riseup is that they are still invite only (they were originally open to registrations but moved to invite only after having abuse issues), that alone should be enough not to recommend them.
They clearly fill a very needed niche, but I don’t think that they should be used as a normal email provider, for activism activities and provided you align with their values it could be a great non-commercial option though.
They are anarcho-communists, their logo is literally a star with the anarcho-communist flag colours.