If the Catholic Church is all wrong, as you say, why would anyone want to be in Communion with this false thing? For that’s what it means, Communion with Christ, including His Body in all times and all places.
And on the other hand, if the Catholic Church’s doctrines are true and her Communion IS worthy of adherence and belief, why would a person want to receive Her most precious and sacred Sacrament illicitly, without being received into the Church?
IOW: it’s a matter of honesty.
If you don’t believe, don’t receive.
If you DO believe, you need first to be received into the Catholic Church, and Holy Communion is one of the Sacraments of Initiation.
And you would be as welcome as the flowers in May!
The "Church" as you state it, is not the Roman Catholic Church. The "Church" is the body of all those who've placed their faith in the redemptive work of Christ.