Making games is a lot of work and hard work. Games require very specialized skillsets and those need to be pulled off on a professional level to actually be "good".
To make something on a professional level requires time. Time is usually money.
Building a single mockup for a game is in most cases not even 1/100 of the work the actual game takes. Same goes for a single animation. The biggest time factor regarding art for 2D projects are animations - most mockups usually don't include any animation.
Making a mockup - no problem
Making some animations - no problem
Staying long enough motivated to get a complete game done - hard
Getting a game done on a high level of quality with barely any funding and no time - we are here nearly in the impossible utopia
If you work seriously on an indie game you want to ship the usual goal is to get stuff done. Working time bought by an individuum is rather "expensive" compared to money provided by huge companies.
In the indie sector most coders pay artists because they usually earn twice the money artists do.
Free coders are the same as free artists - inexperienced starters - otherwise they won't work for free.
In personal stuff an artists pours in time for the idea, the actual design, the sketchwork, the drawing, the final illustration plus all those small tweaks.
That process takes long, established game studios know how much work art is and it's paid as it is.
If you just look up credits on a lot of GBA /SNES games you will see how many people there are involved.
Most people (coders are not excluded) are amazed if they hear how much working time an actual high quality art asset needs.
If you expect a single individuum to pay for that, it's getting really really expensive.
But with cutting time short you can get something done, won't be great but will work and you will get a game done. That's what we actually see if we look at 90% of all indiegames released.
A better funding or a longer development time results in "better" games.
And especially if it comes to development: more is always possible and there is always something which could get added
It all depends on the people involved in a project and if you are getting along well enough to finish the game.
I don't think there is a lack of mutual understanding, the bigger lack is actually in understanding how much work, time and effort the production of the simplest game is.
That just from not having an overview how much work single tasks in different areas are - that goes for everyone.
It's quite easy to put your assumptions over actual research.
If you put here any "not so enthralling game which got released" in, I am quite sure a shitload of hours went into the creation of it.
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I also want to make clear that despite money is a constant problem in game development it's not the thing which saves everything.
All the money in the world can't help to get one's soul on any project. It's pretty much what Ellian described here - there needs to be enough freedom to make something to "a part" of yourself.
One is always ready to make bigger sacrifices for something which is special to him/her.
THat "soul" is something one can actually feel - it's like inspiration or it moves you if you play something - but it's also a very individual experience.
If there is no reward except money for doing something, why not doing it in the fastest way possible to make profit (that's how everyone handles business)
A lot of game development comes down to just be realistic about your expectations.
Especially about being realistic about what's achievable and what's affordable.
But a lot of indie development comes additionally down to an "relationship" level as well and the emotional hurdles. Indie game development can be like love affairs.
There are values for everyone which exceed money, the question is just if those values and goals of a team are fitting well together, or if something is just "work" and not more.
Maybe you should ask some indie people who made indie games you liked how they did it. There are some pretty cool stories out there.