I played until Roark and ... it just felt like Diamond but with minor QoL improvements.
Like, FR/LG removed a lot of the Gen I jank, HG/SS and OR/AS had drastically different look and feels, and even if you didn't like, you have to admit that LGP/E had a very unique take on Pokémon and a vibrant art style.
For better or for worse all of those games felt different by the time you were ready to face the first gym leader, this feels like it was too faithful of a remake that they didn't understand why the original artwork worked in the first place.
There's the Underground yes, but unless you have NSO (and want Internet Connectivity) this pretty much feels like a worse version of the diversity I could get in something like Renegade Platinum.
Personally, this feel like this was rushed (as the many softlocks seem to indicate) and I wouldn't recommend the game to someone unless they very specifically wanted "Sinnoh on the Switch".
If you liked it, I love that for you and I'm glad you're having a blast, but it's just not for me.