When the amount of front your army is capable of contesting is constrained by the fact that you don't have 2-5 sweepers, that is a problem. Now when you send off a bunch of solo units, it is an expectation that you will hit some mines, but those should only force you retreat and concede that area temporarily, not lose an important unit.
*This is really important. Dividing your troops up correctly, and having the micro skill to multi-task them is the single most important skill to improve to get better. Blobbing your shit to cut down on squad wipes is really detrimental to gameplay. Increase skill gap= profit!?!?!
On the flip side, the enemy often has a limited supply of munitions are only a couple of mine laying units at most. If you see things like weapon upgrades, recon planes, grenades etc then you can safely assume he isn't blowing a ton of munitions on mines and can send your sweepers through the most likely areas. If you see none of those things, it'd be prudent to invest in a second engineer for sweepers. You can even put them in a halftrack and still detect mines.
You don't need to blob to counter mines, you just need to make sure your sweepers are roaming through uncharted territory first. You can also not take the obvious, direct path to the strat points so you walk right into the mines.
It's ironic to be arguing for a bigger skill gap when one of the biggest divides between players is how well they sweep for mines and use game sense to avoid critical losses.
In other words
1. Mines punish simplistic map movement. You have to carefully path your infantry so they don't cross through obvious mine spots.
2. Mines punish a lack of scouting into fog of war or the enemy backline. (Both with recon flares/planes to keep an eye on his engineers and sweepers to check for mines.)
3. The skill ceiling is ultimately higher when players have to consider their movement through the map, and likewise consider the best mine placement to punish that movement.
4. On the defense, using mines to zone out and slow down your opponent is a great strategic skill to have.