I have read that book and thought a great deal about this. Assuming there to be an objective material world is very useful in practice. Still there is something even Lenin admits about experience. We can only ever have a subjective view of reality. We know that various chemicals and socially informed perceptions and so on are highly determinative in how we perceive reality. The way machians tried to categorize the world and describe some perfect system is absurd, but they are not completely wrong. I have tried hard to find the right conceptualization for experience and it is ultimately futile. Meditative practices are very helpful in clearing up perceptions to see things closer to objectively.

I highly recommend reading ‘The Ego Tunnel’ and ‘The Mind Illuminated’ for a scientific perspective on Buddhist insights rather than going “philosophy that’s not mine is bad, religion is bad, look away.”