but it also has some very extreme snowballing/slippery slope behaviors If you move games away from mechanics then you push it onto other factors, like economy. If you get an early lead and hold down some key terrain, it very easily translates into more resources, a stronger army, and a much stronger lead that is difficult for an opponent come back from.
One word : Economy.
RTS economies are generally over an entire match. If both players earn resources at a (potentially) similar rate and one player loses units in an early encounter then the obvious occurs – they are at a disadvantage. The solution to this is quite difficult because it involves being able to identify that you are in a bad situation during a fight and being able to break it off to fight another day. In most games that involve player vs player this is a fairly high level idea. Most players simply fight until they die, respawn and go from there. In this way a player losing a fight in an RTS is always at a disadvantage, always on the back foot. This is really just part of RTS but what other economies are there?
I like FPS and so that is what I am most familiar with. You also have economies in RPGs, where mana and cooldowns are the “economy” during an encounter. Games are about interaction of economies.
All games have economies. CS has an economy that last one half but fluctuates round to round. Quake duel has an economy of time that translates into armor/health (resources) a player can accrue and then attempt to kill their opponent. Simply attacking off spawn yields less chance of winning. However the economy here can be viewed as the amount of time it takes to stack to a decent amount in order to contest a large item spawn. If you want two 50a + shards + 2-3 weapons this is about 50s of time spend. You can then “spend” this time contenting the next 100a or mega spawn. This is quite hidden though, as the mechanic requirement of the game is steep, as is positioning.
Overwatch has an economy as well. Each attacking side has a limited number of pushes per round, gated by the time limit and respawns. Ideally teams should all push together, and having a player picked means you need to commit to an imbalanced fight (5v6) or wait for them to respawn. The same applies to the defending team, where a player being picked gives the attackers a numerical advantage until that player respawns and returns to their team. It has other, faster economies around ultimates and cooldown on normal abilities. So we can see that in the context of some popular FPS the economy is not the duration of the entire game but broken down into smaller, bite sized pieces over the course of a match.
Warcraft 3 resource drag and similar concepts have been mentioned, but imo these are not there to prevent snowballing as much as force players to action. If you have a lead then you should capitalise on it before your opponent catches up. It rewards a player that has superior economy management with a limited advantage – the time it takes their opponent to catch up. This creates urgency. It also plays into unit upgrades and spends there rather than simply buying more.
Company of Heroes has squad based infantry and gives the player the ability to “retreat” their units at high(ish) speed to their base where they can then be reinforced back to full strength. This allows players to disengage from encounters that they are not likely to win at the cost of time + reinforcements (if any individual soldiers are killed). This cedes territory to the opponent and gives them time to do other things. Reinforcements are cheaper than buying a whole new squad. In addition there are other upgrades that keep early game units relevant until endgame, both purchasable as well. So by keeping units alive you negate some resource loss when losing fights. You also benefit from keeping the units alive because they are still viable late game. In addition one of the three resources (manpower) is penalised as you have more units on the field.
However it hinges on the aforementioned player requirement to retreat the units, which isn’t immediately obvious and takes time to recognise lost causes instead of just fighting to the last man. Even still the “run away” function is much more reliable and less mechanics involved over other RTS.