SG, what Synod are you with? I'm in the LCMS. I was raised Catholic and have been Lutheran for 20 years.
There are number of very important differences between the two. Most of them can be traced to the RCC claims of the Pope's lineage to Peter, his authority over the centuries, which points to the source of their doctrinal differences: TRADITION
The RCC leans on Tradition for its doctrine, so what the Pope has dictated carries equal weight to scripture. Through Tradition, they have come to hold to Mary's ascension into Heaven, her sinlessness, praying to Mary and saints in heaven as intermediaries, the infallibility of the Pope, and other doctrines. As you know, Lutherans do not.
There are observable differences, too. Catholics rely on interpretation of scripture from the priest, so they don't emphasize Bible study and have no Bibles in the pews. Nor do Catholics bring Bibles to church.
I don't bag on Catholic members, because I do consider them part of the body of Christ, but the institution,... We have more in common with them (the members) than not. We both use a liturgy in worship.
Actually, I could go on with a lot more on both lists. We do have a rule on discussions on RCC doctrine, so anyone adding comments should refrain from turning this into an RCC argument. We can talk about the differences, as the OP asked about.