I hope this is the voice of writers in general, however humble.

Every writer's intention is to share his thoughts.  He doesn't compel the reader to buy or read his book. It's natural of him to write/say this:
'here I am writing what I am thinking and about my experience....'.

But life is never short of philistines.  A few might even say:
' Don't advertise before me!'

That the person should articulate the above shows how low- down he/she is---it smacks of ill-will, ignorance, contempt and spite, immaturity and in the worst case--schadenfreude!

Confucius  the sage (600 BC) wrote about the chun-tze (the gentleman, the perfect person) who is kind, tolerant, encourages learning, practises humility, kindness, generosity, shows respect for all people, and delights in the success of others and never denigrates others as the xiao-ren (the 'small' or inferior person) does.

Confucianism has captured the imagination of the West which has openly declared that the founder was among the world's greatest philosophers.

Was the sage advertising himself? If he were so,  would he have survived for over 2,500 years?

Anyone who dares say that the writer is an advertiser must be among the most deplorable.  He or she should be pitied!