Yeah, I've never been huge on composite sketches. They can guide the public and LE toward a scent, but I've always believed it's one's actions that really brings suspicion upon a person and not a sketch. A sketch is just a jumping off point, a basis. Things like a spouse suspiciously on one night coming home much later than they were supposed to and acting strange. Someone randomly selling their car in the days after a homicide. Someone uncharacteristically breaking routine shortly after a murder. Someone randomly burning clothes in their back yard for apparently no reason. Things like that. A lot of the general public will resemble a composite sketch, but one's actions give actual substance to that suspicion.
And another thing I think sometimes those of us in the true crime community lose sight of sometimes is, because we are very invested in true crime cases, and spend many hours reading, researching, listening to podcast, watching videos, etc... most of the general public doesn't. Most of the public will see a news story or read about it in the paper, and then return to their day to day lives and not give it much more thought. Now, that obviously varies a bit depending on the town, and the smaller the town, the closer knit it is, so you may have a higher percentage who are more aware on the day to day as the town size gets smaller... but most people don't go about their day looking for killers in every interaction they have. So composite sketches really only go so far.
And even if someone like a Richard Allen was walking around town and happened to cross paths and his appearance caught the attention of someone really read up on the Delphi case... what, are they going to report him to law enforcement because he happens to have a goatee? A lot of people have goatees. You investigate everyone with a goatee, you'll be investigating the case til Doomsday. I think Richard Allen wasn't caught until now, because no one ever had a reason to suspect him... until now. Or there were a select person or persons in his circle who did suspect him, but were too scared to say anything.