How to reproduce bug:

1. Hold a food item, torch, or water bucket in your offhand, and hold any block in your main hand.
2. Aim for a space that is currently occupied by a player, entity, or non-full block, and right click with the block in your main hand.

Absolutely nothing will happen at all. In previous versions, any attempt to place a block in an occupied space would cause the player to use their offhand item instead. The old behaviour seems to be more desirable, since it allows for quick consumption of food or placement of torches while mining.