1. Work bot skill up from 70% and hold it at 90%
Bot skill is really their response time and accuracy. At 90% accuracy, bots accuracy is as merciless as most human players, be they in tanks, a FW190 or armed with a M1A1 Carbine.
When playing with bots of deadly accuracy, you'll be a lot more immersed and develop a healthy fear of people firing at you, and thus develop a more soldierly view of cover, concealment and most importantly tactics.
2. Try an approach you haven't before.
It's easy, after playing Singleplayer so often to get used to a routine that works. Issue is, playing that map over and over gets reducing marginal utility because bots, random as they sometimes are, offer only so much variation when you, the player keep doing the same thing. So mix it up a bit. Try taking Meteriya ridge and make a right hook instead of taking on Kidney ridge directly. The battle will flow very differently.
3. Try historical ratios.
Most players of singleplayer know that playing as defense is a turkey shoot -- But that's because you're playing at 50:50 ratio. Try playing 24 vs. 40 bots in St. Vith or Ramelle Neuville. In SPR, there were more like 15 Rangers/Paratroopers vs. 50+ Germans.
Gameplay is most affected by ratios, strategy and skillset. So try changing these variables and give your singleplayer experience a fresh feel.