It's an interesting situation in Ukraine.
Ukraine has essentially run out of artillery shells and anti-missiles. That's not an absolute measure, but effectively Russia is missile striking all the infrastructure in Ukraine, notably power generation facilities, with impunity.
The Russians are also slowly taking territory. You might have heard about the recent fall of Avdiivka, which is officially a win for Russia except that Ukraine made it a very expensive piece of real estate. I've heard one estimate that Russian casualties are 10:1 against Ukrainian, so it's really a win for Ukraine. Except that Russia has so many people it can throw into the war effort it might not make a difference.
On the flip side, Ukraine has damaged several oil processing facilities inside Russia 200 miles East of Moscow. Two soldiers carrying small drones in a backpack can hike across the border, deliver a small munition (probably more than a hand grenade but not much more) right to the vertical distillation column using video feedback for targeting, and the distillation column is an integral part of the process and the most difficult piece to repair.
Ukraine has taken some 14% of Russian oil processing offline using this method, which is a huge bite out of Russia's federal budget. Also, Russia now has to allocate resources to protecting vital infrastructure all over Russia.
Ukraine has also had good luck with water-based drones: put a bunch of munitions on a motorboat with a GPS and video feedback for targeting, paint it black and send it at night, several hundred miles with pinpoint precision to sink a warship. Russia discovered experimentally that all of their anti-whatever guns are intended for incoming missiles and other ships, and so they can't point down low enough to hit a small motorboat within striking range. You have to get the crew to shoot at the drone from the deck with rifles and hope you hit something important.
Ukraine has basically kicked the black sea fleet out of the western half of the black sea using this method.
Of note, these drones are being built in Ukraine by Ukrainians. They're not donations from other governments.
Ukraine now has lots and lots of military observers from various countries across the world looking in on the military aspects of drone warfare, which is a completely new tactic for war. If it takes an anti-missile costing $100,000 to take out a drone costing $1,000, that's an obvious advantage to the side using drones.
And no one has tried drone swarms yet either, and I think that would be the next logical step. Exhaust your opponent's anti-missile shield over the city with one wave of cheap drones, then send in the second wave with incendiary munitions to set everything on fire all at once.
And all for the price of 1 anti-missile missile.