I agree 100%.
Here is the other part, if Nexon thinks that matchmaking currently isn't an issue for 95% of alliances, after implementing this, matchmaking will become the issue almost every alliance will be screaming about. Right now alliances can take on slightly stronger opponents, and it be a relatively even match. By reducing tactic space, the ability to attack up will be harder meaning it will be more difficult to pair alliances in a "fair" or "even" match where each side has a chance of winning (disregarding sandbagging and the current incredibly unmatched wars). Ex: If one side has 2 atomics at the top pairing them with any alliance that has no atomics will be uneven.
Reducing tactics means it will be much harder to successfully attack ESPECIALLY for gunpowder and enlightenment players. If they want to bring new players into the game and have them not be discouraged, this is the absolute WRONG move. Right now, many of younger players struggle anyways if they aren't linked up with allies/community giving good advice.
Barrage will never be effective UNLESS you change it so I can barrage the entire base and kill every living defender in it.
Heal: I know people who have tried to use heal, but hell no am I going to upgrade it to see if it might be useful. And, trading in my carts for a heal seems stupid especially since my troops will be taking more damage because I can't sabotage anything.
At the very least, if you do this, please consider increasing tactic space for Gunpowder and Enlightenment players to 6, and IA and GBA to 8. Although that might throw it off because the ability to take 8 demo or 8 decoy seems excessive.... But, this is the point, messing with the tactic space is messy/complicated and NOT the way to go.
I bet Nexon never asked players about what changes in certain tactics might make them consider using them. No, that would have been the obvious way to do it.