I can all but guarantee you that the people who have contributed to JSNQ have played KSP just about every way a person can. So much so that they extracted all the value they could find out of the stock planet system and started making their own.
You're flying green frog people to space with your keyboard.
Realism is a silly thing to talk about in that context.
At any rate, Tweakscale exists. Module Manager exists. Nothing is stopping you from applying a patch to remove/relax career limitations and just Tweakscaling the parts to meet your own, personal, arbitrary measure of realism
It's also evidence that you are trying to accomplish a mission with parts that are no longer well suited for the task. Or trying to play a planet pack that is not well suited for your personal difficulty preferences.
In the difficulty settings, you can make experiments return more science if progression through the tech tree is too limiting for you. You can also make the missions return more rewards so you can unlock VAB / Pad upgrades. Or you could install some contract packs that will give you kerbalbucks and a reason to go do science experiments on Kerbin to get better parts. Or you could install mods that give you more options for parts. Or you could use Tweakscale and some module manager patches to adjust the career limitations to something more suitable for JNSQ's scale and your own personal preferences.
JNSQ does not claim to offer balanced career mode play.. It claims to be more challenging. JNSQ changes planets. Not parts (well, it changes like.. two parts?). Not careers. Not rewards.
What people find balanced is subjective. There are plenty of people who disagree with you about this.
The stock scale is not "slightly overpowered". Have you ever tried doing a playthrough where you try to recover everything? I have, and I found that I had to design my first stages very carefully to not launch everything above it directly to orbit in one stage in the earlier parts of the game. It's stupidly easy to make a rocket with 4k dV in the first stage for most 'homeworld' missions after only a few tech tree unlocks.
I don't want to make assumptions about you, but I really do think this is a matter of skill or perhaps just being set in your ways. Not trying to gatekeep here, but I managed to do most of my early game 'homeworld' missions using nothing but 1.25m parts. In fact a large bit of them were done using BDB 0.9whatever meter parts.
When in doubt, try making your payload smaller and reducing the scope of what you're trying to do. You don't have to return every payload to Kerbin. You can transmit science instead of returning it. You can do quite a bit of the early career missions using a stayputnik+a gimballing engine. It's annoying and a little more difficult, but it can be done. And you can return those parts + science if you put them inside of a 1.25 service bay with the realchute covering the half of the Stayputnik that sticks out. of the top. Open the service bay doors and you have fins that will help reorient you for reentry.
The challenges that JNSQ sets up are the reason that entire last paragraph exists. Because I never would have bothered to figure out how to accomplish more with less if I wasn't forced to by the increased scale making it more difficult than going to the Mun on my 3rd or 4th launch.
Sorry but that hasn't been my experience with career mode in JNSQ at all. Sure, it's more difficult, but that's kind of the whole point, innit?
They are worthy, and do have a place. At the VERY BEGINNING of the game. In 2.5x+ scale, 1.25 rocket parts are not really suitable to do much beyond launch very basic payloads to LKO. If you're creative you can use them to do a flyby of the mun. If you're creative and persistent you might be able to pull off a Mun/Minmus orbit and return. But that's about as far as you're going to get with them without bumping up against mass/part limits in career mode.
Says you. Also, I'd be interested in seeing a video example of how you do a gravity turn. Because I bet it's pretty inefficient.
I suspect the vast majority of players that are using JNSQ are not only playing with Career Mode, but also with mods that make it harder. I personally play with Unkerballed Start to force me to use probes instead of crew. And with reduced DSN power (relative to JNSQ scale) and greater occlusion. I also play with part unlocks that cost money, with no crew respawn, and with 80% science rewards because of the added experiments that mods add.
Again, the entire point of JNSQ once you get beyond the breathtaking improvements to planets is to make the game more difficult.
And the last point I just made seems lost on you.