Hardly make an argument for it, should we remove the flamethrower from pioneers and engineers because they have mines? Should we remove the zook from SP since they also have mines?
M20 is meant to be build for early aggressive play but it can't do it anymore since it doesn't come anymore enough early and can't defend itself if the lieutenant isn't nearby.
You're comparing one of the worst upgrades in the game (sturm pschreck) to mines that can 1 shot light vehicles like the puma and luchs and immobilize anything larger including heavies. I think there's a disconnect there.
Trying to kill an M20 without 2x rak/pak cheese is difficult if you don't overextend with a 222/luchs/puma. The same way it's difficult to kill a sniper as USF/OKW without a designated counter. I'm not the best player in this game, but I don't usually lose the M20 unless I get outplayed, cheesed or start diving with it.
My biggest gripe with it is that I have to tech into full LT which is mediocre in teamgames because then I have to pay extra to get the OP as sin pak howitzer.
They still have a use in team games. You can't always keep armor from getting behind the front lines so the M20 mines on roads sometimes save low-health tanks or mobile arty. I get them more often when I can't get regular doctrinal mines. The AA on it is really good after it is vetted up. They're also good at keeping MG's on your flank from getting flanked.
They also help end mismatches faster and can be really good if your opponent doesn't know how to counter.
If I had any complaints about it, it would be that they should have reduced the cost of the skirts down to around 20 munis after taking away the bazooka.
I love it in teamgames. Almost no one expects to hit M20 mines against USF unless they see you planting them or they're actually decent and sweep before sending in tanks.
I think the skirts are expensive, but the only thing USF is buying is weapon upgrades and grenades. Taking away skirt pricing to any extent means faster BARs/zooks which can just give USF an earlier powerspike, something they currently do not need.