But we can't stop inflation altogether, because witnesses need it as a reward and SPS is funded with that, right? So we are talking about the reward pool, am I right?

I can see the argument, but the good thing with inflation to authors and curators is that it improves distribution, which is a big problem, so I've heard many people say. It also incentivezes participation on the network, and now that EIP has taken place, more good actors are getting rewarded, which furthermore improves distribution and devalues some inactive ninja mine stake that might be out there. This is good for the long-term health of Steem I believe.

I think we first have to see the long-term effects of SMTs before doing radical changes to inflation. I could see allocating more of the inflation to SPS as a valid idea, but getting rid of STEEM reward pool I don't think is a good idea, for now at least.