If you have not personally attended a mass you would not know what it is actually like. I have found that to be similar in nature to the assumptions of some Christians who have no personal experience with Jewish assemblies. Is it a sin for you to attend either Catholic or Jewish assemblies ?
Ephesians 5:11 And have no fellowship with the unfruitful works of darkness, but rather reprove them.
Jewish synagogues include no paganism. I still don't attend them as they have been set aside by God "until the time of the Gentiles" comes in.
I don't have to catch Ebola to know I don't like it, now do I? Many will say that is over the top, but if the Roman Catholic Church is really what we believe, spiritually I am spot on.
I have found that to be similar in nature to the assumptions of some Christians who have no personal experience with Jewish assemblies.
But in my case at least, I have attended Roman Catholic houses of worship during a variety of observances on several occasions. Found there to be a very hocus-pocus atmosphere.
Is it a sin for you to attend either Catholic or Jewish assemblies ?
Attend? Probably not. Participate? Probably. But the Roman Catholic Church forbids my full participation anyway, so not sure where you are going with that.