Why have any laws, even the Ten Commandments, if there’s always “wiggle room”?
Because the intent of the Law was to lead us to Christ, not to save us.
It's meant to show us God's standard and our need for redemption.
If righteousness could be gained through the Law, Christ died for nothing.
Application of any law requires discretion. For example, if 6 year old shoots his brother out of anger, the killing is objectively wrong. However, the wiggle room is the child is considered to lack full knowledge of right and wrong.
One can come up with other countless examples where there is an objective evil, but is mitigated by some circumstance (wiggle room).
The challenge regarding remarriage and Holy Communion is whether any discretion exists, and to what degree it should be exercised.