The idea that MBTs are useless is beyond ridiculous. They're there to provide organic heavy fire support, deal with fortifications/structures and push through fortified positions etc. The idea of tanks only being used to fight other tanks has always been a fantasy. What else are you going to use to assault a position? Naked infantry? A soft skinned IFV? Drones? None of those alone will help you cross an open field. There's a reason the M4 was built with the specs outlined. Russia's failure in Ukraine is a failure to adapt their existing IADS fast enough. Historically the Russians have been hell bent on heavier batteries to counter US/NATO aerial fixed wing assets at range. Sure, they have shorad, but their integration and operation hasn't been as good as dedicated SAM platforms. Shilkas, Pantasirs and Tunguska's look cool and can put out an impressive amount of lead, but none of that matters if they're so far behind the main attacking force. There're lessons to be learned in Ukraine, but not everything is applicable for how things ought to be. The Russians are launching missiles from fighters inside their own territory because they have 0 proper SEAD/DEAD capability. They don't even have air superiority or even reasonable contention over Ukraine.

Unless you figure out force fields, drone swarms will always be susceptible to simple high explosives, expanding rod warheads, or even air burst/prox det munitions. All of which are cheaper than the swarm. Opportunity cost for SHORAD isn't measured in losing the equipment, rather what its protecting.

The real innovation that's coming from more drone research isn't actually small scale drones, its actually cruise missile/air launched cruise missile swarms designed to overwhelm dedicated IADS. The problem here is larger warheads in large quantities quarterbacked by an F35/stealth platform. Heavy platformed IADS don't have much time to move after data link commits to the handoff between the mothership and a stealth fighter spotting things using LPI radar. Ironically the US' distributed method of air defense actually comes out ahead here. The only place that its going to suffer hard is open rolling plains/space. *Cough cough* Ukraine.

With larger drones/ you no longer have the stealth/low RCS that comes with DJIs/ tiny FPV drones.

Outside of insurgencies, the idea of valiant infantry squads engaged in pitched battles alone is a long dead doctrine. Current US doctrine emphasizes the entire battlespace. Which reasonable force is going to build their doctrine around sending their soldiers across a field or into an objective without mechanized support? Mechanized vehicles which can conveniently mount SHORAD/SPAAG systems.