We have been playing Minecraft since 2012. Since then, a large number of new items have been introduced. For example, new types of (non-cobblestone) stone now spawns, and new non-stackable wood products.
Over time, this has led to an imbalance. That is, by exploring the same distance in a Minecraft world, one's inventory now fills up significantly faster.
Consequently, this leads to excessive backtracking to item storage areas, and takes away from the immersive Minecraft experience. Items such as the Shulker Box and concepts such as the Llama caravan could have mitigated this, but are somewhat cumbersome (or difficult to obtain). Thus, inventory sizes should be correspondingly expanded, and/or additional methods of easily carrying more items should be considered.
This is not a bug, and shouldn't be reported as one. However, there are much better ways to store items for easy movement. It is just later in the game, through the introduction of shulker boxes.