No. See Wikipedia: Marketing is the methodology of communicating the value of a product or service to customers, for the purpose of selling that product or service.
Marketing is about communicating the value of the product. Regardless of the actual quality of the product. Building a great product is not marketing.
"Marketing is the activity, set of institutions, and processes for creating, communicating, delivering, and exchanging offerings that have value for customers, clients, partners, and society at large."
Marketing is _not_ simply about communicating the value of products. Advertising something that doesn't help a customer create or experience value is not marketing.
I think you'd find this article and the comments interesting:
Good marketing teams will evaluate your product VS the competition and use the good parts for communicating the message. Amazing teams will also take the bad parts and bring them up to the product teams so they can confirm weak parts and put them in the queue to get looked at.
Marketing a bad product will only last so long.
Building a great product is most definitely part of marketing. For example there are methods and techniques which faciiliate it and are subject of marketing journals and marketing academia. One of these methods is the "segmentation-targeting-positioning" framework.
I can get you many more citations if you wish, or you can spare me the time, and search for them yourself. Perhaps you will learn something of value in the process.
This thinking can occur because often entrants to a competitive marketplace will assess their competition, identify a weakness and deploy a product to meet the need. The development of the product in this scenario is not 'marketing' as you assert.
How would you build your product if you don't know what the market conditions are? How do you find out what the market conditions are? By segmenting the market by behaviour/need/price sensitivity, then targeting a segment which is underserved (or you can serve better), and finally positioning your product to cater to that particular segment with specific product design, messages and distribution channels.
Marketing doesn't develop the product. It just designs it (writes the specs).
Maybe in start-ups or 1-product companies. Even then, this is not a good practice. Your customers will make a choice between you and competitors/substitutes. The product team does not know or understand this process. They don't do choice modeling, they write code.