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Old stars were really big, and the universe used to be smaller. Your assumptions would be closer to correct in the pre-solar, or pre-galactic universe when universal expansion forces outpaced gravity, but as the universe cooled down, gravity took over. You can group current stars by the stars they were formed from based on metallic content. There was enough matter in stars 2-3 solar generations ago to form dozens of Sol sized stars. Normies will refer to the post nova clouds formed by these stars as "stellar nurseries", but they're just stellar corpses. Heavier elements fused by the stars during their fusion and nova stages are what the planets are made of, but because stars go nova once they start fusing iron, a relatively small amount of a star's mass is anything but hydrogen before the end of their main sequence.
The amount of matter you see in planetary accretion is incredibly small, usually under 1% of the mass in a solar system. Gravitational resonances between planetary bodies can shift the bodies toward, or away from the star inside the accretion plane, or out of the system entirely. These same forces lead to formation of proto planets which form their own accretion discs in orbit of young stars.
