Ask IH - "no go" problems or ideas?

Hi fellow IH’ers

I would love to hear your opinion on 'no-go' ideas/problems/segments of market etc. Based on your experiences, observations etc what problems/ideas seems very appealing on the intellectual level but close to impossible businesswise (in context of indie hacking).

My takes:

• new email client - very high number of base-line features, huge players on the market… and working with email is still painful
• dev tools - in general I mean not (fully) open sourced dev tools

PS: I hope the whole idea of no-go will be more an inspiration than a warning (hacking means something after all :))