I imagine many active scientists have something of a (gender neutral) "nostalgic science boner" for this period of time, and discovery
Consider the cost of psychology's stance on introspection:
Armed with nothing more than the lens of introspection and metacognition, and their own keen perception and intelligence, each psychologist was able to extract essential features of "the mechanics of cognition between the brain and behavior", and to draw rational conclusions about them
@themanual4am Hurry for gender-neutral science boners. ;)
I'm not sure what you mean by "psychology's stance on introspection," but it certainly is interesting to compare your statement to the paragraph about cells.
One big problem with introspection is that you can only apply it to a single, human mind. Those folks studying microbes in pond water had an incredible variety of examples! They could make statements about single-celled life generally because they could see patterns across species.
When it comes to minds, we're at a huge disadvantage. It'd be great if we could start by studying simpler examples, but we can't. The best we can do is study brains and behavior, which just isn't the same.
This is great! We fundamentally disagree! 
A great opportunity for some daylight on the case for introspection, please pushback as much as necessary
Perhaps first, let's make sure I'm talking to the right points!
1. why is the big problem so?
A side note: I suggest that we can study a simpler mind (than commonly experienced), by establishing a baseline (of zero interpretation), and incrementally isolating and mapping all context and content phenomena separately
@themanual4am It's problematic that a person can only introspect their own mind because it limits their perspective. They cannot experience first hand what it is to have another mind. They especially cannot imagine a mind of a non-human shape. This means we can't use introspection to do what those early cell biologists did: compare many diverse examples to find common themes and variations. We don't know in which ways our own minds are "typical," or what the range of mental experiences is.
Your point about observing a simpler mind is an interesting one. You're suggesting that we simplify our own minds, observing simplified activity, or a subset of activity. That is a powerful tool, but it's not the same as, for instance, observing what it's like to have the mind of a bat. Or a nematode. :)