I need more buttons/grouped buttons to micro manage my army... 10 is not enough! SERIOUSLY

Yes, this is an issue but it is an increased issue for players not native to the AoE realm. Many players have units rallied to a location and will simply drag a box to select units from there or use keys as shift or control to take (specific) units from there. Others may use the select all army combination. In both cases it can be usefull to select, or unselect, units from the UI at the bottom. However, this has its inefficiencies.

These inefficiencies are more detrimental to new players and players coming from other games as this feels very unintuitive to say the least. Except for those accustomed to AoE games already. The current way of dealing with it simply needs additional clicks and it only allows you to adequately micro units in the region your screen is focussed. The current mechanic is worsened that if you add clusters of units in proximity to the same group they will align in a formation and all have reduced speed. Well, all except one: the slowest one.

For the latter I made a case in a separate thread: allow us to toggle unit formations on/off. The thread can be found here: [Formation] Add movement formation toggle

In part this would solve the issue as grouping units together will not be detrimental to their base speed anymore. A much welcomed feature as currently slow religious units (but also boats?) are clustered in when you hit select all army. One could argue it be nice to have a select all infantry, cavalry, siege or sea type of functionality. However: that would not fully resolve the issue as bombards serve a different purpose and positioning than mangonels and landsknecht have a very different base speed than spearman. And one should have a balance between having options and having a digestible amount of options.

I have no perfect solution but I do feel your issue. I quite often opt to simply refrain from making to many types of units simply because they become impossible to micro when selecting all army, locating them on the map, or adding / removing them from specific groups.