Let's face it; the modern brigade is the equivalent of World War divisions. We could simply rename them divisions, for they aren't much smaller than the Russian idea of a division anyway.

You need a combined arms team including
* the capability to penetrate MBT frontal armour (AT),
* the capability to shoot building-destroying shells in direct and indirect fire (105mm HE and greater),
* the capability of electronic reconnaissance (triangulation and monitoring) and radio jamming,
* the capability to deploy enough infantry to search a large village or fight your way through a forest road,
* the capability to sustain the force itself for at least three days without major supply deliveries
of a much smaller size than a brigade or division.

The really, really interesting formation is therefore rather a mixed and reinforced battalion (battalion battle group / Kampfgruppe) with a three-digit head count
and
for missions that emphasize economy of force and reconnaissance the correct size would be a mixed company (this one would then substitute infantry with a dismount scout platoon).

I understand that the approach of "pure" administrative units is still widely preferred, but I don't get why a formation such as a brigade has even today still only one TO&E.
It should have several ones:

An early training TO&E (training within units; equipment proficiency, typical unit missions, reaction drills).

A late training TO&E (advanced training in mixed battle groups).

A Battle group / maneuver team / Kampfgruppe / fighting column type of TO&E for a combat-heavy land campaign.

An occupation / blue helmet TO&E.

A skeleton self-defence TO&E (support units serve as makeshift infantry and AT troops, original combat units down reduced by attrition down to a third by assumption).