No matter how similar Lutheran teaching is, it doesn’t approach the same level as Catholic teaching, because Lutheranism, as a Protestant religion, is inherently wrong. Also, Lutherans don’t have mass. Only the Catholic church has mass.
This is how attending other religions’ services works. It’s okay occasionally, but not past that. Why? Because attending, say, a Lutheran service regularly will make people think that you are now “one of them,” that you’re “in communion” with them, which is wrong for you to be. And, slowly, over time, this relationship will start to work in the opposite direction, in that you will develop connections to them and start to identify with them. That’s bad for two reasons. First, you potentially are involving yourself with a heretical religion, causing your soul to go into jeopardy. Second, people will start to talk. They’ll say stuff like, “Oh, he was Catholic… Now, he wants to be Lutheran.” That looks bad for the Church. People will probably say that I’m being “mean” or something by saying these things, but I don’t care, because it just makes sense. You have to understand that Protestants as a whole are extremely critical of the Catholic Church. I mean, that’s what “Protestant” means, a person who protests the Church. I am a former Baptist. Protestants will try to ensnare you in their “teachings” and try very hard to wean you off the Church. They may even place undue social pressures on you to abandon your Catholic faith. They will say something like, “Oh, the Catholic Church is wrong for [this poor argument] and [this poor argument] and [this poor argument],” and over time, it will be very tempting for you to cave in so that you will “fit in.”
Oh and, do NOT receive their “communion.” Lutherans believe that what they are receiving is the Body and Blood of Christ. They believe in the True Presence. But a Lutheran priest can say the Words of Consecration all day long, and the bread and wine never become Body and Blood, ever. Their priests don’t have the power to do that. So, first of all, their communion isn’t real. Secondly, think for a minute about what “communion” means. It means to be in commune, or close association, with others. By accepting their “communion,” you are not only receiving just bread and/or wine as opposed to Christ’s Body and Blood, but you are affirming that you believe in their beliefs, that you profess what they profess, that you are in communion with them, which, as a Catholic, you cannot be.
So, please don’t start going to a Lutheran church.