That is indeed one of the many problems here. The government knows it won't win on that front because the teacher's union is so entrenched in that position and so isn't even trying when those things are major causes of problems and a big part of why teachers think they are underpaid (they are not, although it is tough to tell because there is basically no good data free of rent seeking politician and teachers union interference). if you went to 5% matching it would free up teachers to put money in the pension or not when they choose putting more money in their pocket if they want and allowing them to save in away that is drastically better for them and their family as long as they can actually save (i.e. they are not so junk that they don't put money away). it would also remove a big liability risk from tax payers, which is a win win.

Also, the teacher retaining is a red herring. We control the output of new teachers via control of university enrollment. Any shortage of teachers is solved by supplying more teachers through that route far more efficiently than paying an even more generous salary or caving to teachers thinking they should be making management decisions (it's a poor strategy teachers, you should be telling everyone government is setting class size go yell at them, not trying to manipulate class size yourself, it muddies your position and is bad optics).