Is it ethically right to build a product that I know might end up as a rip-off, especially because these products already influence my design and thinking?
It's like Coca Cola and Pepsi. Just keep the look and feel / label different to avoid confusions. If you want an example in software, think about MS Office vs Open/Libre Office.
I am a similar situation as you also working on a similar product. Here is what I would ask myself:
- Are you intending to copy them?
- Is their product particularly novel?
- What are you doing differently? Price, UX, features I require, integrating into different API's, etc.
I would highly focus in on differentiation, what makes you different from them? Are they too expensive, so you are disrupting their market with a comparable lower cost option. This is how a free market is supposed to work in a capitalist society.
Edit: Formatting