If you lived in the star trek universe what would you change ?

I don't watch Star Trek, and only know stuff through pop culture / memes.
I'd IMMEDIATELY BAN TELEPORTERS.
Becuase they are MASS MURDER MACHINES
I'd find its inventor(s) and put them on trial for crimes against humanity.
- Calm down Barkley, they're totally safe.

Stop sending administrative officers on away missions. There are specialists for that.
- This is a change I can support!
  But flagship captains are still allowed to disregard the prime directive, right?

Incredible advancements in science! Blindness? Cured. Missing limb? Here is a mechanical one so good you can’t tell! And since there’s no currency in the Federation everyone can get everything they need.
Id get a full body check over for any and all issues and probably be some mad scientist somewhere playing with wild anti gravity forces.

I'd be so gobsmacked to escape capitalism that I don't think my imagination could catch up with me. I imagine some of us would be back in the holodecks reimagining it due to Stockholm syndrome.
- Never watched the show. I wonder how they select who lives in on ocean front of California cost, who's on the second row and who's 30 miles from the coast?
- "Computer, load program 'Bear Stearns in 2008'"

Seatbelts for star ships!
- And circuit breakers or fuses. Stop storing fireworks in the control panels.
- Good call! And maybe we tie the boulders in the bridge ceiling to something, while we're at it.
  I could almost go as far as not routing incredibly hot plasma through the helm officer's control panel, but I think I love tradition too much.

I would have a deep meaningful conversation with two betazoids at the same time.

Ensuring that the Starfleet admiralty suffered... transporter accidents... and got replaced by somebody -- anybody -- with some kind of clue would be a good start.

Holodecks as every home! Who needs furniture if you can live in a holodeck and summon furniture based on your needs or wants at any given moment? And why limit it to furniture? Furnishings and decor could also be holo'd! And beds, and windows, and could you Holo a Replicator to replicate any food you want? Feels like the possibilities are endless
- Maybe the whole thing is in a holo deck in some nerds basement. He's just pretend exploring the universe all this time.
  
  That's an episode of Black Mirror, right? Lol.

Would like never jack off
(Holodecks are affordable right?)
- What do you mean affordable, the federation is post scarcity
  
  Post-scarcity doesn't mean that everyone can have everything, though. It just accomplishes the goal of UBI, satisfying basic needs.
  I'm only about 3/4 of the way through TNG so I am probably setting myself up to be corrected, but it's not like you can simply replicate things like a personal starship or a palatial mansion in the mountains. Some people still have assets with inherent value which are relatively exclusive.
  Replicators allow everyone's basic needs to be met—to live comfortably, even—but it seems like some goods still need to be either rationed selectively or distributed based on merit. People still "own" things; property still exists. People still work jobs that they hate, so there must be a reason they put up with it. Some Federation citizens also still turn to crime, indicating that they desire more than the system otherwise provides. And even with the abolition of traditional currency, the concept of generational wealth still exists, as we see with Picard's family estate.
  Regarding Holodecks in particular, they seem like things that normal people have access to, but they don't seem to be common in homes (at least from the examples I've seen so far). I assume it must be something like movie theaters: most people use public ones, while bigwigs might have their own they can use whenever. And anything that is public must be time or resource regulated in some fashion, so at some point someone would order you to leave so others could use it.
  At least based on what I've seen so far, it seems like an economy still exists within the Federation, just a more abstract one than we are used to seeing in the real world.
- They definitely cover that in Lower Decks: https://youtu.be/-YeTDrk5ayw

Give everyone the ability to control their individual genome. Why should we still be “humans”? I want echolocation and night vision to start. I understand the implications of genetic manipulation and why it’s outlawed in the federation, but if EVERYONE can do it, I think it becomes a non-issue.
- This comment right here, Section 31 officer.

Ruin it by making it into the Elite Dangerous universe.
Who cares about exploration and protecting emerging civilizations when you can make funny images with the galaxy route map and participate in huge system control wars for void opals lol.
Or give random items to Thargoids for a totally scientific process of investigation.

Introduce the God Emperor of Mankind from 40k, sit back, and let the fun begin.