Apps aren’t divided into “high-traffic” and “toys.” There are plenty of use cases where you have a low-write server in a production environment, and SQLite would work fine there.
If you need high write volume, then yes, the locking behavior means SQLite is not a good fit.
SQLite can easily hit 15k INSERTs per minute or more (setting processor affinity to a single core helps drive the max rate up). However, if a process begins a transaction and then stalls, it halts all dml.
I think performance can be good, as long as a competent schema design is in place. Allowing ad-hoc queries from less trusted users will surely tank performance.
If you need high write volume, then yes, the locking behavior means SQLite is not a good fit.