Agreed on most counts.
The difference between D&D "grenades" and XCOM/modern grenades is that the former are typically glass flasks, for which it's reasonable to shatter on contact instead of bouncing. Now, of course this is a separate issue from being able to throw an object 10-20+ meters upward. 5e RAW says the range of Alchemist Fire Flask is 20 feet, which is much more reasonable (when accuracy matters).
Strong +1 that climbing ladders should require movement. One of the main benefits of high ground should be that it takes a while for enemies to reach you. My Misty Step shouldn't be countered by your ability to essentially teleport up a ladder. I'd be fine if ladders costed normal movement, but would prefer if they (and all climbing surfaces) took double movement. And if you don't make it up, you end your turn on the ladder.
You should also be able to block ladders, either by standing at the top or the bottom of them. The enemy would have to shove you to get past. That'd introduce some cool tactics.
