Does my product have non-substitutability?

This question is essentially asking if your product has a "moat." That is, what do you have that others find difficult to imitate or surpass, allowing you to maintain an advantage in competition? This doesn't necessarily have to be groundbreaking black technology; sometimes, it's just subtle details.

You can consider the following angles:

1. Are the switching costs high?

Simply put, how troublesome is it for your users to switch to another product? This trouble could be money, time, effort, or even emotional attachment.

For example: You're used to WeChat; all your relatives, friends, and work partners are on it. Even if a chat app a thousand times better than WeChat came out now, would you switch? Probably not, because the cost of migrating all your relationships is too high. This is switching cost.
Ask yourself: If my users stop using my product, what will they lose? Is it the data they painstakingly built up? Is it the operating methods they've grown accustomed to? Or is it the real money they've already invested? If they can easily "walk away," then your product lacks irreplaceability.

2. Are there network effects?

Simply put, the more people use a product, the better it becomes and the greater its value.

For example: Taobao. More buyers attract more sellers to open shops; more sellers mean richer products, which in turn attract more buyers to browse. This is a positive cycle. If you want to create an e-commerce platform to beat Taobao now, it's extremely difficult because you don't have that many users initially, so the value can't take off.
Ask yourself: Is my product great for a single user, or is it even better when everyone uses it together? Will the addition of new users improve the experience for existing users? If the answer is yes, then you have the potential to build network effects.

3. Do you have unique technology or resources?

This is the most hardcore "moat"—you have something others don't.

For example: DJI drones. They have deep technological accumulation and patent layouts in flight control, gimbals, and image transmission. Others who try to imitate them either can't bypass these patents or produce something with significantly inferior performance. This is a technological barrier.
Ask yourself: What is my core competitiveness based on? Is it a unique algorithm? A supply chain channel that others can't access? Or a highly influential brand? If your product is just a "combination" of existing technologies and features on the market, then the likelihood of being replaced is very high.

4. Brand and user mindshare

When people think of a certain need, your product name is the first thing that comes to mind—then you've succeeded.

For example: To search for something, use "Baidu"; to drink cola, buy "Coca-Cola." It has transcended a mere product and become synonymous with a category. This kind of mindshare occupation is something money can hardly buy.
Ask yourself: What image does my product have in the user's mind? Is it a "cheap product"? A "professional tool"? Or an "indispensable helper in life"? Can this mindshare positioning be replicated by others?

In summary:

Don't always think, "My product has the best features." In today's world, this is rarely a true barrier. Feature leadership can only last a few months at most.

True irreplaceability often lies beyond features:

It makes users "reluctant to leave" (switching costs).
It "binds users together" (network effects).
It has "unique skills" (core technology).
It becomes the user's "first thought" (brand mindshare).

You don't need to excel in all of them; as long as you go deep enough in one or two of these areas, your product has a chance to survive and thrive.