I think you answered it yourself. I don't think what people are siting as reservoirs being a better solution is inherent that nilson reactors are flawed. I think that the approach in which we use a nilson reactor had been ingrained to force us to think that way. It also doesn't help that people watch videos and take what was said as truth.Aside from space constraints, why does anyone use a Nilsen reactor over a reservoir?
I've been using a nilson (kalk) reactor without any of the negatives that are said to be true from the popular talking heads on social media. I've concluded that the only difference is preference. Do you want to use a reactor or a reservoir? It comes down to preference. They both require different maintenance routines, and which one fits your needs is the one best for you.