- The candidates could pay/ask someone else to do the assessment for them/* and prepare a presentation.
- You are assuming candidates are willing to dedicate time to complete your take-home project. If your company is an unknown/smaller/boring company, good candidates won't bother to go through the process.
- Phone screens and or system design white-boarding, etc... only require 45mins - 1 hour from the interviewer to assess a candidate.
All interview techniques are flawed and there is no clear winner. FAANGs, for example, prefer the algo/design interviews and they do have hard data to work with, and clearly that have worked for them.
That said, I think you will succeed. Very simple, straightforward site. Seemingly neat integration with Greenhouse. And clear pricing structure.