Indie Development: Self Made vs. Store Bought vs. Originality + a few updates on projects

In Zombie Sleepover, we recently hit a major road block, all our assets are store bought and we do not have an artist to change the textures or models but as the bought assets are nice and popular, a lot of developers are using them. It is fine for small things but if the sample levels from the content creators are used in games unaltered, they go a bit too far.

There is a huge package for medieval caves, dungeons and castles on the asset store and we found at least three games on steam and on other platforms with the same assets, even with whole level segments copied from the samples provided. I do not own the games, so I do not know if the content creators are credited enough and I do not know what the right way to credit store bought assets is frankly, shall I list all the packages I bought or not? Do I do that only if I do no alterations on the assets?

Store bought assets are fine for prototyping and if you are able to change them to make them fit your game better but using them unaltered in the end project seems kinda cheap but we were thinking of doing the same thing just because we do not have the artistic skills required to make out own 3d art or the textures like in those packages. As that stands, do we have a problem and need to hire an artist or is it ok to use those assets and make the game we want with generic assets but with our game play and level ideas? Will our game be less original as a result? Is it possible for a programmer and a sound designer to make a game on their own without going the "artistic minimalist route" or do crappy pixel art (not that all pixel art is bad, there are some really good pixel artists out there)?

Due to negative feedback on Zombie Sleepover and the amount of games with the same assets, we are changing the concept for the game to be something different (more on that later, as soon as we are done with the redesign). That will result in a change in our projected timeline, meaning the game has to redesigned a lot and we do not know how long that will take.

In the meantime, I am working on a few things in Dork Tales and hopefully get back to streaming on a more regular basis and keep it up this time (hopefully)