but it's often overly wrong, and not very convenient; thus the fact that you can't safely import subroutines into an OO module feels like a design bug to me.

For convenience; and to solve the problem at coding time rather than burdening your users with runtime solutions, try:

package utils;
use Exporting::Module qw[ utility_sub ];
package Your::OO::Module;
use Exporting::Module ();

...
utils::utility_sub();
...
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