But then, in a good market, how does a poor rookie pilot get enough experience to get a job?

By towing gliders, flying skydivers, flying as an instructor, performing fire monitoring tasks (?), joining small companies which offer multi-engine and/or multi-crew experience etc. Much the same regardless of the market? You probably know more about this than I do.

IMHO it depends on the person’s aptitude, and to that effect they should develop tests capable of accurately determining that. I don’t believe such a foolproof test exists right now. Reminds me of a guy at a job interview, when asked about his past experience he replied, “If past experience was so essential, they would never have put a man on the moon!”. He got the job. 😀

AFAIK, pilot aptitude tests are in use by different air forces, some civilian FTOs and a number of airlines/operators. The tests are not necessarily “foolproof” but they may aid an examiner in obtaining an impression of a person and his/her aptitude for pilot training. Such testing can e.g. indicate the rate at which a student pilot should be expected to make progress.