Friends hi-fi system not very good, what do you do or say?

I may as what they like about it so they can share the reasons for their choices but unless they ask for advice, I'll just say it sounds pretty good.  It's a safe answer.  :D

Always a polite and positive comment unless the friend specifically asks me to critique their system.

What’s the purpose of the music?

we all have different meanings and taste 

Music is the ultimate drug. It can change your mood,mindset, feelings, personality or emotions in a moment. Our biorhythm get in tune with the beat, chords, vocals and the overall experience. Add in the lyrics and it grabs our soul. The music that lines up with our heart beat, breathing, blood flow, and life beats become or favorite songs.

pls don’t judge 👩‍⚖️👏👍🙏😂

I would say, "That's a really interesting system.  Tell me about it!"  That steers the discussion to how he acquired the equipment, what he likes about it, etc.  People love to talk about their gear.  If he comes over to your house and *asks* to hear your system, let him hear it.  He might be just as "polite," or he might say, "Gee, I like this better," in which case he might ask you to help improve him own system.  

Try to admire what he's accomplished or purchased.  OTOH, if he starts saying "Come on over and we'll do some listening!" then at some point you're going to have to be honest and say that *your* system suits *your* ears better.

I had a dear friend who passed away a while ago.  He had a fabulous record collection, but I never thought his system was all that great.  But I enjoyed having beer/wine with him and talking about this and that, so I let the music spin, made positive comments about the record and the musicians, and left it at that.  OTOH, one of the best musical evenings I ever had was with a lovely gentleman who had a terrific 78 rpm jazz collection and an old KLH Model 12 system with speakers stuck here and there.  Didn't matter a bit, the music was fantastic.

I would say I really like your system and that I have been really stupid to spend so much money on my system and here you have a really nice system. I just wanna listen to music and enjoy that after all.  I wish I was smart as you.

And then they ask you what you have in your system, and of course that’s really what I wanted to express anyway but I did it in a cute sort of way. And then he’ll be complementing me on my system saying I bet it really does sound pretty good you shouldn’t be critical of yourself. Can I come listen to it?

Then I would say if I had to do it all over again I would just buy an integrated receiver with basic speakers and call it a day and be just as happy. Now I drive myself nuts trying to learn more and more and recognizing I really haven’t learned much at all. Truly frustrating experience to pursue this and never get to a point where you’re satisfied with anything. and Looking at my car and saying wow I could’ve done a lot better.

And then the guy is basically providing me comfort for my awesome system and he hasn’t taken offense while we mutually have a common understanding at this point that his system probably isn’t as good as my system. And now he’s envious of me and that’s just fine.