I think it's too early to say it's failed to replace the existing systems programming languages and its trajectory looks positive. For example, in the 2019 Stack Overflow developer survey[1] only 3% of professional developers reported using Rust. A year later[2] it was 4.8% and a year after that[3] it was 6.4%. So in two years professional developer use doubled, by that metric. For reference, in the SO surveys C++ and C use was about 20% and 16%, respectively and, if anything, slowly declining (as a percentage of respondents, of course).