You are asking for contributions from people and at the same time, you have plans to "monetize" the website by building premium-only features. It feels like exploitation.
No it doesn't, cause there's a massive amount of work that goes in projects like these and there's costs too. Costs that donations don't always pay.
Would you prefer a huge banner while you're browsing asking you to donate and telling you that if we don't meet a certain quota we're shutting down the website, or would you prefer having an additional feature that you may or may not want to pay for? I don't know you, but I'd definitely go for the second one.