I ask this because I think of the recent switch of Ubuntu to the Rust recode of the GNU core utils, which use an MIT license. There are many Rust recodes of GPL software that re-license it as a pushover MIT or Apache licenses. I worry these relicensing efforts this will significantly harm the FOSS ecosystem. Is this reason to start worrying or is it not that bad?

IMO, if the FOSS world makes something public, with extensive liberties, then the only thing that should be asked in return is that people preserve these liberties, like the GPL successfully enforces. These pushover licenses preserve nothing.