I think the real problem is that the rules of grammar are changing, and things that are acceptable now were not always so. This means some one using the older grammar rules reading modern text would say it is bad, when in fact it is not.
For example, the use of "shall" is almost completely gone from American English, so sentences where "shall" is the correct word we now use "will." This would be bad grammar under the previous understanding of what "will" is used for.
So, IMO, good grammar will always be important, just what that means will continue to shift like it always has.