Hey there,
Yes, 21 months is a bit on the lower end for an MBA, an MSc in Marketing, on the other hand, can be a tangible option.
In terms of curriculum, MBA as the name suggests, will have core courses that are focussed towards all aspects on business administration, which a choice of electives that will allow you to specialize in marketing.
MSc in marketing is a program with a more intensive take on Marketing where the core as well electives will be focussed on the micro and macro aspects of marketing.
A lot of MSc marketing programs will go deep into the trending industry concepts like big data analytics in Marketing as well as application of marketing in major sectors ( Retail, heathcare,etc.)
Here is a quick comparison between the MBA and MSc Marketing curriculum of the same school:
MBA
Core Courses
NegoSim Business Simulation
Problem Solving and Communication
Financial Accounting and Reporting-Bach Business Game
Financial Markets
Managerial Economics
Marketing
Statistics and Business Analytics
Giving and Receiving Feedback
Gender Balance Seminar
Corporate Finance
Ethics and Sustainability
Management Accounting
Operations Management
Organizational Behavior
Strategic Management
Key Specializations:
Digital Innovation
Sustainable and disruptive innovations
Strategic Management
Advanced Management
Marketing
Finance
Strategy
Entrepreneurship
MSc Marketing
Big Data
Business for Business 1: Creating Value, Switching to Solutions
Business for Business 2: Gaining Access and Engaging Customers
Business Plan
Consumer Behavior
Consumer Intelligence
Digital Marketing
Managing a Career in International Marketing and Sales
Managing Innovation for Growth
Marketing Fundamentals
Marketing through Social Media
Pricing Strategy
Retail Marketing and Distribution
Sales Force Management
Strategic Brand Management
Strategic Marketing Simulation
Electives
Corporate Social Responsibility and Marketing
Data Analytics
Health Marketing
Inbound Marketing : Evolution or Revolution
Luxury Strategies
Managing a Parisian Fashion Brand
Neuroscience & Marketing
NPISim (New Product Introduction Simulation)
Depending upon how intensive you want your course to be, you can make a pick.
In case you need any help with school targeting, here is a list of some of the top MSc Marketing programs across the globe :
https://www.mim-essay.com/blog/msc-in-marketing/Hope this helped