There are many shortcuts. You can recycle assets by using the same enemies with different level design to bring new challenges to the battles, alter textures instead of making whole new models and use lighting to create a different mood and context for environments when using the same basic blocks. A robust level design tool is essential when creating a content-driven experience and well worth the initial extra effort.
On the other end of the scale, you can also go with less content heavy and more mechanical experience. This approach is common in roguelikes, which use runtime procedural level generation to create a new experience for each session, usually using the same assets as before. Another example is puzzle-roleplaying game hybrids such as PuzzleQuest which rely heavily on their battle mechanic and leave the story content to the background.
How well a mechanics-oriented game works depends heavily on the balance of the previous axis. Since you lack the opportunity to hand-design new challenges using the same assets, the game s core mechanics need to support a wide variety of choices and emergent challenges. Failing to provide a compelling enough core mechanic makes the game feel grindy and frustrating.
One thing that I ve noticed lessens the feeling of grind is having some secondary objectives. It feels less frustrating to hack through dozens of enemies if some other meters go up along with your XP bar.
Axis #3: Story vs Freedom
This axis is somewhat related to the previous one, but more from the perspective of the narrative experience. As with grind, the story is content and as such expensive to produce, but roleplaying has had an interactive narrative as one of their core tenets from the very beginning, and the whole genre is as much a medium of storytelling as it is a form of games.
Whether fairly linear games with a great story are better than open world games with an emphasis on player freedom is mostly a question of taste, although the real classics manage to find a very delicate balance between the two. However, the ones that do are more often than not gargantuan products with budgets of tens if not hundreds of millions.
For any smaller game, you need to have few tricks up your sleeve to balance this. One obvious option is to scale down the fidelity. If you have your story as mostly text and the art is relatively low-resolution 2D, you can fit in a lot more content with fewer resources. Another is to recycle the assets you have: instead of a story choice leading to different places with a different cast of NPCs, slightly tilt the content in a single place and use the same characters. Telltale was a master of this sleight of hand: the outcome was mostly the same, with the only difference being which character did or said what. The X remembers this was also a neat trick that made a choice feel important even if in reality it had little or no effect to the actual outcome.
You can go too far to another direction too. Modern Final Fantasy games are not exactly known for their free-roaming gameplay, but Final Fantasy XIII managed to take this into an extreme that scared off even the hardiest fans.