I may have some concerns in the area of immersion / historicity, but in terms of gameplay mechanics, I like just about everything that has been revealed. The new systems may or may not be implemented well, impossible to tell without playing, but going by the descriptions I really like them.
Navigable rivers - a popular item on the player wishlist since forever, this opens up a whole new aspect of maps.
Removal of worker units - a personal favorite, I've wanted to see Workers/Builders gone since I experienced CtP's much better flowing version. Workers can be done well, they have not been done well in Civ, they suffer from what I term the "decision-implementation gap". Glad to see them gone.
Specialists instead of moving citizens - you can now decide on permanent boosts to your urban tiles, which replaces the citizen swapping system that's existed since Civ1. That is a good thing, the citizen swapping was potentially the biggest source of minmax micromanagement in Civ and eliminating that improves the design by a lot.
Trade routes and resource effects - most of this is implementation-sensitive so I'm cautious but I like what sounds like a major improvement to the trade system. It's interesting to trade for resources that do specific things, rather than everything being one of the base yields. Cities apparently have resource slots, and all in all I think this sounds like a more interesting resource system.
Commanders packing up units to move - this is just brilliant. The best design choices are ones that are unexpected but massive improvements, I'm pretty sure this is one of them. 1UPT as a basic concept is completely fine, as many games show. Both in Civ5 and Civ6, the 1UPT implementation has a major problem with traffic jams. They're annoying in the UI, they make getting your troops to the front lines a harder puzzle than actually defeating the opposing military, they mess up the AI pathing so the AI typically underperforms compared to what the tactical AI is capable of. A very promising improvement.
Crises - demonstrated to work pretty well in Stellaris, having sensible crises is a good idea. Every Civ game to date has you at your weakest on turn 1, then you keep getting stronger from turn to turn. Civ6 Immortal/Deity guarantees you'll be attacked on turn 10, at which point if you can fight it off, you continue getting stronger. Having a major crisis appear is a good idea to break up this pattern, and is even historically sensible as real civilizations haven't had the luxury of constantly increasing prosperity.
Tech mastery - for the first time in Civ, there's something else to do with science except for getting deeper into the tech tree. It doesn't seem like a huge change but the new decision of advancing in tech vs deepening your mastery of current techs is surely going to be interesting
Diplomacy - with how the influence system is described, it's clear there are some game theory mechanics at play. No idea how good it will feel in practice, but I already appreciate the departure from 20+ years of the bargaining table
Independent people - every Civ game has had barbarians. Civ5 and 6 have city states. The way Civ7 combines those into smaller independent tribes that may or may not develop is a very logical next step for the design
So while there are definitely non-mechanical aspects of Civ7 that concern me, just about every mechanical change in Civ7 sounds like it should be good.