Yes, most of experienced runners' running is at a conversational pace, often literally (this is why running groups are popular).
To explain why harder isn't better: improvement in running comes only a little from muscular strength, so that mental model is bad.
Improvement is primarily based on aerobic development of the cardiovascular system. This is your body's ability to burn mostly-fat with oxygen, deliver the energy (ATP molecules) to muscles, and remove waste products. So you develop more capillaries, your heart gets literally stronger, and this fat-burning pathway gets more efficient.
Going too hard pushes into the anaerobic zone (burning sugar without oxygen). This is good training in some ways, but it can be counterproductive to aerobic development and, most important, it's too hard to do very much volume so the amount of stimulus is limited. By keeping it easy, you can do a higher volume of purely aerobic stimulus.
I have been exclusively an anaerobic athlete for the past two years and my aerobic fitness has dropped to a shockingly low level. But I am oddly comfortable at 180-190bpm
I am slowly building in more aerobic cardio into my training but man cardio is just such a chore for me. It's always the first to go so it takes constant maintenance and it's time consuming...
I’ve seen this happen. We call it having great cardiovascular fitness but not so great metabolic fitness. One of the reasons that zone 2 or maintaining aerobic fitness seems to have such an impact on longevity is that it requires and reinforces metabolic fitness.
To explain why harder isn't better: improvement in running comes only a little from muscular strength, so that mental model is bad.
Improvement is primarily based on aerobic development of the cardiovascular system. This is your body's ability to burn mostly-fat with oxygen, deliver the energy (ATP molecules) to muscles, and remove waste products. So you develop more capillaries, your heart gets literally stronger, and this fat-burning pathway gets more efficient.
Going too hard pushes into the anaerobic zone (burning sugar without oxygen). This is good training in some ways, but it can be counterproductive to aerobic development and, most important, it's too hard to do very much volume so the amount of stimulus is limited. By keeping it easy, you can do a higher volume of purely aerobic stimulus.