The Resistance is also nothing more or less than the continuation of the old SSPX position, which dates back to the very beginning of the Crisis in the Church (and hence, is legitimate).
What we must have primary loyalty to, is the Catholic Church. Well, the Catholic Church was undermined and taken over by Freemasons in the 1960's. So enter "The Traditional Movement".
So for Catholics living in 1970 - present, our first loyalty must not just be to "The Catholic Church" but specifically the Traditional Movement. We reject all errors including Modernism, but also the various errors contained in dogmatic Home Aloneism ("the Traditional movement isn't legit", "You can't just set up chapels without permission", "we must avoid the Conciliar Church BUT ALSO all so-called Traditional chapels", etc.)
If we are to love the Church, we must love the Church in our own age. We must love the Liturgy, the Mass. We can't reject our only options for experiencing that Mass in our own age. Keep in mind this Crisis has persisted 52 years and counting. The dogmatic Home Aloners have basically been proven wrong -- proven to be foolish and stupid in their opinion to reject the Traditional Movement and "wait it out" -- wait for God to end the world or whatever. Even if THEY MIGHT HAVE BEEN RIGHT in the beginning, the last 52 years of history -- hindsight -- proves them to have been wrong *all along*.
In my opinion, such dogmatic Home Aloneism is *more* dangerous for one's soul/salvation/family than "doing one's best" in the Conciliar Church. Just for starters, there have been Indult options for decades now, which takes the evils of the Novus Ordo Missae out of the equation. Everyone knows my opposition and problems with the Indult -- but I must say, it's far superior to dogmatic Home Aloneism.
I am a firm believer that the Catholic Faith is "a habit of life".
I also believe that the SSPX was the most popular Trad Movement option for so many Catholics for various *good* reasons, not base ones. Yes, more people prefer the Broad Path to the Straight and Narrow Path. But the majority of people also prefer water to urine, as a beverage. So the majority is NOT automatically wrong.
As I've said before, if you take 100 men who have given their lives to follow Christ (arranged their lives, homes, career where they can be practicing Trad Catholics), who fear God, put Christ first, and have already to-date made thousands of sacrifices -- if you take polls among those 100 men, you better believe I'm going to pay attention to the will of the majority! Because not all majorities are created equal. Heck, the Catholic Church Herself goes by majority vote on who should become Pope. But it's the majority of CARDINALS, who have presumably given their lives for Christ.
+ABL had his priorities straight: resistance to Modernism, formation of true priests. Everything else happened by God's will after that (setting up a professional network of chapels, etc.) That was all a testament to +ABL's prudence and wisdom in how he set up his organization, his Rule. But also: +ABL didn't go one step further than he needed to, i.e., demanding everyone adhere to this or that opinion on the Pope, the Crisis, etc. Which is proven by the fact that even as recently as 2015, plenty of sedevacantists attended SSPX chapels.