Grenades allow infantry squads to wipe support teams very easily due to their pinpoint accuracy. If heavy machine gun teams take cover they clump up and are left vulnerable to being instantly wiped by a single grenade, this makes relying on HMG teams against blobs of infantry incredibly dangerous which goes against their intended role.
How is that a bad thing?
Unless you mean throwing grenades from a plain HMG facing blob, in which case the solution would be to make blob much more vulnerable to suppression.
Demolition Charges ironically encourage blobbing; the constant threat of instantly losing a full squad means it’s never safe to send a lone squad out to cap against Soviets without the safety of being escorted by a minesweeper. Instead, players can be forced to blob cap only around their minesweeper, especially in the late game when the loss of vetted squads is so punishing. Demo Charges only counter blobs if your opponent is foolish enough to neglect sweepers. If Demos are only plantable on buildings and bridges then they would still serve a tactical purpose, but without discouraging players from lone capping.
We may not have the same definition of blobbing, but having your minesweeper with a regular infantry unit, isn't what I call blob.
Demo on capping point isn't something you just spam, and get a complete success rate everytime you plant one.
Demo charges offer various tactical possibilities, limiting it to buildings only is going to make it so boring and predictable, and instead of not being prompt to capture a point, you will just discard every garrison until you minesweep it.
Other than that I pretty much agree with LMGs and the current light vehicle meta, some changes are needed here, not only to fix blobbing either way.