There should be something like special perks that you can buy with XP, so you can choose to delve deeper into specific specialization optimization as opposed to starting a new specialization. Examples: A Gatherer could spend XP on a Perk that gives them the ability to swim deep into the sea scour the sea floor for unique sea food ingredients. or A Carpenter could spend XP on a Perk that allows them to recycle furniture into some of its base cost. or A Farmer could spend XP on a Perk that allows them to craft special seed mixes that can mix 2 crops on a single tile. or A Smelter could spend XP on a Perk that allows them to [refine] tools to give them an extra layer of durability. Giving the player to make the choice to dig deeper into their profession or get a new star would encourage even more player collaboration too.
I do feel like part of this issue is the XP gain curve. I think if it would drop off more sharply it might encourage more late game XP optimisation. Maybe further splitting up late game jobs would be an alternative.
This has been partly implemented in Update 13 through the star cost of talents and will be expanded in the upcoming Update 14 with a star cost for applying modules to work tables. Further uses will follow in future updates.