Would have preferred to see things tweaked the other way, taking away the ability to put a mine on any hill, and making mines like quarries, something that require a resource to mine before you can build one. Lumber mills should have been left as something that's only useful along a river, a location that has a lot of competing uses for districts, etc. Overall production could have been boosted through buildings that boost worked tiles of particular types combined with a general across the board cost reduction (in terms of hammers; gold and faith costs could remain as they are). Also, lumber mills are every bit as unappealing as mines in real life. No reason for them not to carry the same appeal penalty.