I vote for higher resolution Planetary textures including night lights for Earth and cloud layers for the appropriate gas giants to fly through.

@DarkDust great points tbh, i agree
on a relevant note, the thing that always bugged me is that unlike KSP we can't place down flags on planet surfaces which is kinda... sad i guess? it's possible to kind of recreate this by saving launch locations in sandbox mode, but ever since we got the ability to teleport our crafts to planets, that became a rather pointless thing to do

Having started with Juno a few days ago, here are my thoughts as a KSP player with almost 800h on Steam:

For me, the lack of tutorials was quite frustrating. Without prior knowledge from KSP I would've given up quite early. Especially for people who don't know about orbital mechanics and things like that it's probably very hard to understand what's going on. For example, if I remember correctly I was asked to put a craft in orbit at a certain inclination early on, but there was no explanation what an inclination actually is and how to change it.

Right now on Steam, only 8.8% of players managed to get into the SOI of Luna or Brigo. That means 91% of players have given up before even reaching this (IMHO small) goal. Only 23.6% of player have reached orbit! So more than 75% give up before even getting into orbit. That's something the developer's should be worried about, new players need to get more explanations/tutorials.

Juno has lots of great parts, the editor is great, ability to "script" your crafts to automate tasks is great, etc. But a lot of it feels disconnected, and yes, is missing some charm (IMHO). There's not that much incentive to do something, like earning science/tech points: KSP has lots of small rewards, like do an EVA to earn a few science points, etc. In Juno, the rewards are for larger tasks so you don't get a reward as often and sometime actively have to seek out things to do on your own as the missions (even with "progression") often don't give a reward except money.

I also miss some map of the solar system showing all my current crafts. Like, I have a craft on longer journey to Vulco, next burn is in a 100 days or so and I want to do some missions in between. I need to actively remember which crafts are on active missions, click through them in "Resume Flight" to check their state, as there is no overview of any kind.

So yeah, the game is great but IMHO is missing some quality-of-life features and needs to better guide new players. It has a lot of potential so I'd love to see it get some improvements.

Planet gravity!

It would be cool if the made planets have gravitational effects on each other depending on the distance, This includes moons or binary stars, Planets! Etc.

Planetary collisions.

Planets colliding with each other, And each time a new planet is created with the combined mass of both worlds, Also and worlds that collide will be added to you list in PlanetStudio.

They could make Juno New Origins, A mini version of Universe Sandbox 2.

Its difficult to say why exactly the game hasnt reached a wider audience, but an aspect that definitely plays a part into it is the fact that the game is quite deep, with a fairly steep learning curve. The procedural parts and powerful editor are great for making anything you could imagine but for the average player I can see how it could easily lead to an overwhelming and frustrating experience. Another aspect that has been mentioned by many ksp players specifically is that the game doesnt have the same "charm". And while in some sense that is a cop out answer for not liking the game because it doesnt look and play the exact way ksp does, there is some truth it. A large part of the game including ui, music, sfx and models do give off a certain cold sterile feeling and I can see that being a little offputing for some people. In short, some of the aspects that make the game great to begin with also have the side effect of limiting mainstream appeal (the way I see it).

@Zenithspeed Well said, thanks. Hoping the game sees better days. Really hoping more people see how awesome it is, I basically can play it wherever on my phone, save a sandbox then continue on a PC if need be.

i've been wondering about this too, i think the main reason as to why it's unpopular is simply cause KSP is such a giant that it just completely overshadows it
i think making the game more user-friendly (more/better/detailed tutorials, sample crafts, etc.) would help a lot in keeping players, as few reach a skill level high enough to really appreciate this game or even openly praise it like i do (i do some very small, free, completely unofficial advertising for JNO on some game forums i'm on, and i really do think it's that good, it's basically my number 1 favourite video game)
however the lack of updates right now is probably what's causing it to be kinda "dead" at the moment (it is like that 99% of the time though), for now the devs are working on SimplePlanes 2 so it's understandable
however, i also think that if JNO gets popular enough to get its own Wikipedia page (needs to fulfil their notability criteria and whatnot) like SimplePlanes did, it'll be smooth(er) sailing from that point on