Every workout you do needs to have some kind of focus. Whether it be technique, speed, a specific energy system, heart rates, effort, recovery… you need know what you are doing and why you are doing it. Without focus, you’re not getting everything you can out of your training.
Swimming a practice with generic intervals and no speed requirements doesn’t make sense. There are a lot of generic workouts that give meaningless intervals or rest requirements. I say meaningless because it is a “one size fits all” solution for a complicated problem:
If a person is told to do ten 50s freestyle on the 1:15 or :15 seconds rest, what does that mean? How does that help a beginning athlete who is coming in on the 1:14 or 1:13? How does it help an experienced athlete who can hold :35s with little effort? The beginning athlete is probably struggling with lactic acid build up, which is a completely different energy system than the experienced athlete, who might be getting too much rest to help their aerobic base improve. The workout is the “same,” but both athletes are getting two different workouts out of it because the instructions are too generic.
It is okay to ask what your target heart rate should be. Don’t be afraid to find out what the goal of the set is. If the workout you are doing doesn’t ask you to focus on something specific, either use the resources around you or put the onus on yourself and pick something. Don’t be afraid of focusing on the wrong thing because there is no “wrong” thing. The more you think about what you’re doing at practice, the less you have to think about it during a race.