The only way to raise your tech level in SplinterFaction is to upgrade your Commander. Nothing else does it. So what happens when the Commander dies?
In 1v1: you lose
Immediately. It doesn't matter how good your economy is or how large your army is. This is deliberate — the Commander is a strong unit that gets stronger every tier, and it should feel dangerous to use. The trap is that it feels safe long after it isn't. Use it to push, then bring it home.
In a team game: you keep playing, frozen
The match ends when the last Commander on a side is destroyed, so your team fights on. But you keep every tech level you had, and you can never gain another. Lose it at Tier 1 and you're building Tier 1 units for the rest of the match while everyone else climbs to Tier 3 and 4.
That sounds fatal. It isn't, and the reason is the army-wide weapons and armour upgrades. Those RP tracks don't require a Commander, and they apply to everything you own and everything you build. A player frozen at a low tier can pour all their research into them and field lower-tier units that hit far harder and survive far longer than they have any right to.
Some time back, in a team game, I lost my commander at Tier 1 because I wasn't paying attention. I used T1 units and mass weapons and armour upgrades to stay in the fight. Killing T2 with buffed T1 isn't exactly efficient, but it let me stay in the game and help my team win.
That's the intended shape
It is not efficient — you'll spend more to kill less. But it keeps you contributing, and in a team game contributing is the whole job. If this happens to you: stop mourning the tech tree, dump everything into weapons and armour, and become the player who grinds down what your allies are too busy to handle.
Two smaller design choices back this up. Tech is permanent — once you have a tier you can never lose it. And Commander weapons are mostly ineffective against other Commanders, so a game is never decided by one lucky meeting between them. Your Commander bullies armies, not other Commanders.