Your issue, if the light is "dim" (but working) MAY be: i) a bad electrical connection which reduces the current to the bulb -- i.e., it's "dimmed"; or, ii) the lens has been yellowed by UV degradation or is just dirty (less likely).
In my experience, an incandescent bulb isn't necessarily less bright than an LED light. I think old fashioned incandescent bulbs are more "forgiving" in terms of compromised electrical connections, and moisture.
We replaced all of our Nav lights with LED's EXCEPT for our combo steaming and foredeck light. This year, after 21 years, the steaming bulb gave-out and we replaced it.
Our NAV Lights are Hella's, I think they are the most durable and sealed the best.