You wrote:
“I attend a non-denominational and we have communion (Eucharist) every service. Catholics don’t have a monopoly on it.”
You have “communion”. We have Christ for communion. There’s a difference.
You THINK you have Christ for communion, but Christ was only sacrificed on the cross one time and that was sufficient for our sins (Acts 4:12; Hebrews 10:14). Christ is not re-sacrificed every time Catholics have a mass.