TotK is a very good game. Personally, I’m not a hardcore gamer, I only play a few games, mainly due to lack of time, but TotK is much more complete than BotW.
Yes, practically the entire BotW map has been reused. There are differences, sometimes small, sometimes bigger. What I mainly notice is that the part that also happens in BotW is more complete. More complete in terms of things, in BotW I often had the feeling of wandering through empty parts: climbing over bare expanses of rock walls, and running through vast fields of grass with little to no visibility. I haven’t noticed it yet in TotK. Colors may also be brighter and more contrasted, making the overall look more saturated.

In addition: an entire part in the air has been added, as well as a huge part underground. This underground part is very extensive and exploration must be done partly in the dark. When the towers are above ground, you spend a lot more time underground mapping everything out. I think a factor of five is longer or more.

Besides, there is a lot to do. More tasks, more options, more possibilities. It is possible that TotK is three to five times bigger than BotW in terms of potential game time. And there’s a lot of it that’s really well put together. I only caught a glitch once, but other than that it works very well.

The only thing I’d like right now is to upgrade the master sword so it gets stronger (continuously), which was possible with BotW’s DLC. Other than that, I don’t need anything extra (for now) and hope the time the team can invest in DLC will be used to create the next generation of Zelda. I hope it takes less time, because although TotK is a great game, it is six Released years after BotW. And that’s quite a long time for the second part, which reuses almost the entire BotW map.