Let's use a (bad) human analogy...
Earth is like someone smoking, drinking alcohol, and eating junk food for ages. Of course someone like that will face some health problems sooner or latter.
We are here.
Now, there are these obvious alternatives:
1/ Stop smoking and drinking, get a good diet, do some sport. ( = cut CO2 emissions)
2/ Continue with the same life-style and take tons of drugs to counter the negative effects of it. (= geo-engineering)
The second solution may work for a while, but on the long run it just doesn't work, period.
the only sane alternative is:
3/ Adopt a sane lifestyle AND use a moderate amount of drugs to help a little bit to go back into the limits.
So, geo-engineering can't be a long-term solution.