Anything that is unorthodox is sinful by definition, just make sure that you use the definition that the Church uses. However, a lot of of opinions and behaviors are just personal choices and as long as they do not contradict the teachings of the Church they can be acceptable. We must also consider that some behaviors that could be acceptable in some circumstances might go directly against the virtues in other situations. The bottom line is that just because we do not like something that does not mean that it is sinful, you will never get the totality of people to agree even on simple things when personal preferences are part f the decision process.
Please forgive me, but…

maybe an example would help… although it may come out as bit of a rant…
Anything that is unorthodox is sinful by definition, just make sure that you use the definition that the Church uses. However, a lot of of opinions and behaviors are just personal choices and as long as they do not contradict the teachings of the Church they can be acceptable.
I really didn’t want to cite an example, but… before I do… please know it is my intention to learn - not cast aspersions…
I am Roman Catholic, but I’ve recently taken an interest in a Byzantine Rite held at a local church. The Byzantine Rite is an Eastern liturgical practice started by Saint Basil, who is a Doctor of the Catholic Church. The Vatican approves this rite, and they themselves pray for the Pope and local Bishops in their service.
When I first started going to the services, I didnt really know what I was looking at, so I asked the Deacon. He explained to me that is was all okay to be Roman Catholic and attending a Byzantine service, but I gave him a somewhat puzzled look. He explained “But we aren’t orthodox…” And he was right to say as such, for there are departures from the ordinary Roman Ritual, such as children (even babies) can be communicants.
So my question is - if they are approved by the Vatican and at the same time unorthodox, then how can they be sinful? This makes no sense.
The bottom line is that just because we do not like something that does not mean that it is sinful, you will never get the totality of people to agree even on simple things when personal preferences are part f the decision process.
My point is
not to judge anyone here -
I’m actually trying to do just the opposite. But every time I feel like I can just go to church and enjoy a service - especially if it is new and interesting, or in my own Roman Rite – too liberal (I am a lousy liberal; I have tried and it just doesn’t work for me) – I keep running into this question of orthodoxy.
Take my Spiritual director. I went to him because he is a Jesuit, and Saint Ignatius wrote much of the Theology surrounding the Discernment of Spirits, which is expressed on page one in the Catechism. I figured - if you really want to discern your faith from a Catholic perspective, then who better to offer counsel than a Jesuit? And, with 60 years service to the church - even rising to the level of something like a Provincial - and being a teacher of Theology at several leading Catholic universities - I figured he’s a pretty good guy to be seeking Spiritual Direction from. He’s also a very kind and gentle guy. But some people are giving me flack now about modern Jesuits being criticized for being “unorthodox”. The Priest I’m referring to has never been anything but helpful to me, yet one of the Centers he setup has been called into question by some people.
He’s a very liberal Priest. And I’ve seen other liberal Priests (Redemptorists) who are trying to do something kind for people get criticized for their expressing their thoughts. Terms like “moral relativism” start flying around, and “disservice”, “invalid
name your sacramental blessings”… and so on…
I am a moderate conservative, and it’s really quite disheartening to hear such accusations. I LIKE a lot of those liberal Priests, so - it really hurts when people start coming down on them like that… Aren’t we supposed to be forgiving? Don’t we have Christ backing us up as our Redeemer? As a Priest - wasn’t Christ himself a bit “unorthodox” to his contemporaries? Thus, they said, “This talk is hard to bear…”
Please forgive me here… It’s just I dont see - even as individuals - how we could know every last rule in every Papal Bull ever written… I’m an Extraordinary Minister, and they teach us - “even at communion accidents happen” - people sometimes drop a host, for example, and then what? There are rules as to how to handle an accident, but situations can vary so much - you just have to kind of improvise. I can only imagine what it is like for some Priests who have to give Forgiveness and Spiritual Direction in the Confessional. It may seem liberal to be so kind and forgiving, but then that’s just part of their job…
Am I making sense here? Sometimes it seems one just has to be “unorthodox”, and I dont see how that could be equated with sin at all, especially when the Vatican approves unorthodox services such as the Byzantine Rite, and accuses modern Jesuits of being “unorthodox” when the founding principle of their whole charism sits on the front page of the entire Catechism.
Somehow maybe all our feeble wits just break down in the end… That’s why we’re in the forgiving business, no?