Normally I'd say that reddit/lemmy are poor choices for a community - but if the competitor is a live-chat like discord? Yeah. Lemmy is better.
Project leads would just need to make sure to direct users straight to a specific instance that allows instant/unmoderated sign-ups, or else that element of friction will occur -- and certainly not start the whole "there's many instances, pick the one that's right for you!" spiel, or users will give up immediately. I thought similarly about matrix - on-boarding users to a matrix community would be helped by explicitly writing a guide for them to do so, but then we're back to step 1, where making a discord channel is quicker than writing instructions.