From all angles, I believe the whitepaper matters whether in the case of ICO or IEO, because in each case, whitepaper is used, and it is in this whitepaper that the team writes down their ideas or use case they are bringing to the crypto space. In addition, it is through studying the whitepaper will an investor be able to make the right choice. Lastly, irrespective of the fact the whitepaper is very important, I think most scam team has made it look like it no longer had value, through writing one thing only to end up developing something totally different and of course worthless. So, let's look beyond what the team are projecting, be it hype or whatever and starts from the basics of the project which is found in the whitepaper.
Whitepaper is still an integral part of any project. However, a serious investor should not rely on how well-written the whitepaper is, but check for their capability of delivering their actual product or service. Nowadays, I prefer to check the product rather on how they created their wp. Because most of them are just copy-paste from other's work. So in my opinion, whitepaper doesn't matter the most for me but the actual product they can offer to the community.