This is a common sentiment, but it rarely holds up to closer scrutiny (such as measurements...). Swift is both slow to run and very slow to compile. Both compile and runtime come with extremely high variance. Such unpredictability is arguably even worse than just plain slow performance.
[1] https://web.archive.org/web/20190402100249/https://benchmark...
Incidentally I've spent considerable effort on this problem, including writing a prototype faster JSON parser in Swift (still about 3x slower than Rust, but a huge speedup over what's there). I couldn't get anyone in the Swift community to care enough to motivate me to finish the work, which is indicative of a deeper problem: Swift just doesn't have "performance culture," the benchmark game results notwithstanding.
fannkuch / pidgins: essentially the same
binary-trees / fasta / Mandelbrot: ~ 1.5x slower
spectral-norm / reverse-complement: >= 2x slower
k-nucleotide / n-body: ~4x slower
regex-redux: 45x slower