All I can take away from this is "why is a 20 something hipster" playing in a classic rock cover band??
Because it's a gig seems like an obvious reason.
The cool thing about a trio is the amount of room there can be. Doesn't mean you have to fill every open space but you can if you want to and more importantly,if that's what the group wants to do that's up to them.
Opinions about what other musicians do in other groups are obviously okay to have but don't miss the overriding fact that it's not you and you aren't in that situation. They clearly aren't playing for you, n offense... they're playing for people who dig what they do. Simple.
If you're not on the same level chops-wise get thee to the woodshed and work it out. THEN should you find yourself in a situation like his YOU can show the restraint that you think he should have.
I had a houseband gig where a guy I knew showed up often (never played) and expressed his opinions about me to a friend of mine. He didn't like my tone, didn't see why I "needed" so many different basses, wouldn't have played the song like I did, etc.
Didn't bother me, I figure haters are a natural by-product of doing something right

. And bottom line, one of us was getting paid why the other was watching

. So when I needed a sub because I had to be out of town... I asked him.
Fast forward to the night of the gig. My flight gets in before the club closes and because it's on my way home I stop by. As I came in the door he looked at me from the stage and raised his bass up as if to hand t to me. On the break he told me how much easier what I was doing seemed from the audience than on the stage. He'd been struggling most of the night.
So I do what I do... and don't worry about what others do. If I find myself critical of another bassist's work I immediately ask myself if it's based on envy. Envy can be a motivator just like many other things. I fondly remember a TBer stating
When I get in conversations with bassists who have a problem with other bassists' takes on things it usually doesn't turn out well. I hear people complaining because the BP is playing a song on an X bass when the recording was done on a Y bass and while I get it in an anal retentive way if I'm playing a song I'll play it the way "I" play it on whatever I choose to play it on. And IF I offend a couple of bassists out of the entire audience... who cares? Playing for a couple of bassists vs. doing the gig, the gig always wins for me.
