I believe that Gerhard Cardinal Mueller deserves much more wholehearted sympathy and support from orthodox Catholics than he often does get.
At a time when his Eminence is having to struggle to maintain orthodoxy at the heart of an unsympathetic regime, he cannot afford to be attacked on the grounds that he has failed to defend the magisterial documents of Vatican II in his dealings with the SSPX. So his current praxis is to edge close to de facto reconciliation, step by step, rather than to make a big public splash. His Excellency Bishop Fellay was given faculties to deal canonically with an errant SSPX priest; Society priests can absolve with undoubted validity; the recent rules with regard to Marriage do provide, in a somewhat tortuous way, for Society priests to conduct Marriages which diocesan tribunals will not find it easy to annul; and (most recently) the Society's bishops are allowed to perform "illicit" ordinations (!). (Giving it the power to incardinate clergy from outside itself might be a valuable next step.) There is much to be said for such an approach.
Surely, "step by step" is also a policy which has the advantage of preserving the internal cohesion of the Society. Given the importance of this admirable Society in the work of evangelisation, that is no mean consideration. And, as long as there is no formal canonical reconciliation, there continue to be no restrictions to prevent the Society from setting up missions in dioceses where an obstructive Ordinary might not want them.
With regard to Amoris laetitia, Mueller has made clear that a change in the Church's teaching and practice with regard to "remarried" divorcees would be so monumental that it could not be done by an inference embedded in a footnote, but would have to be done explicitly. As I have several times explained, there is more than one way to skin a cat. Mueller has maintained Catholic orthodoxy, even if his way of doing so is not the way that some others deem best.
And his Eminence is a resolute defender of the important dogmatic fact that Episcopal Conferences, and their Chairmen, have no doctrinal, ecclesiological status: an insistence at the very heart of the crucially important Ratzingerian teaching about the ontological priority of the Universal Church. This teaching is our great bulwark against Kasperism and its disciple Cardinal Marx. Without this insistence, which is one of the most important monuments of the Ratzinger years, the Catholic Church, in purely human terms, would face the same slide into fissiparous heterodoxy which has destroyed the once proud Anglican Communion.
And, not least, Cardinal Mueller has recently pointed out, publicly, that the current regime fails to live up even to the rhetoric of its own PR machine ... as in the matter of the unfair treatment of Vatican employees, who ought not to be sacked without proper and decent process. To do so is the action of an Absolute Prince in a Renaissance Court!