One of our toilets refills VERY slowly - takes 15-20 minutes after flushing.
Assuming the old valve was replaced for just not shutting off &amp; this is only happening after the new toilet valve went in. Then yes, it's debris in the line that ruined the new valve, likely from operating the shut-off valve. The toilet valve should be replaced again after flushing the supply line while opening &amp; closing the shut-off valve to make sure all debris is gone.

You may want to turn the house main down a bit, you just want to flush the line (turn on a faucet closest to the main) &amp; turn the main mostly closed so the faucet drops its flow to half but not less, you still want to scrub out the debris pretty good.

***** THE MAIN may also have debris so remove the faucet's aerator &amp; operate the main until water runs clear.*****