“None of this is dogmatic, but it is in accord with the implications of the Tradition. “.
In other words take it or leave it but either is OK. Also it built not from scripture nor from traditions but it is implied from tradition.
Take it or leave it, pretty much. If de Montfort leads you some conclusion that is contrary to dogma, definitely leave it, or seek a teacher to get you back on the right track.
If he leads you to Christ, then definitely take it.
de Montfort is not dogma.
Same with deSales, Francis Xavier, Ignatius of Loyola, St. John of the Cross, St. Augustine, St. Teresa, St. Catherine, et. al.
Perhaps there is some misunderstanding when some think any Catholic writer speaks for the Church and what they say or write is dogma however the reader may understand what they said or wrote.
Not true.
Maybe this is part of our differences.
We don’t believe we are in this alone; certainly not in it alone with books or texts. We are a teaching Church, in all the forms that teaching may take. We have spiritual directors. Each individual is different, each is, well, individual.
Some people are experiential, more internal, some or outward, compassionate or externally focused, some are intellectual, some are not. We have a wide variety of practices and teaching developed over many centuries.
de Montfort may be right for one, wrong for another. Aquinas may be perfect for one, useless for another. St. Francis of Assisi may open one heart to God; St. Augustine another.
No one is advised to go it alone, but to seek others in community and in individual spiritual direction, all with the same fundamental belief: seek and you shall find.