There's a lot of pressure on product managers to launch the products at hand. However, once you're behind the curtain, you can see what mistakes are being made. It is not easy to communicate your point of view when everyone around you is in a hurry for their success. But this article will help you spot some things.
1. Not marketing the product

Despite being one of the most important roles in any company, few PMs actually do much marketing of their own. A good marketer will always find ways to introduce your product into the marketplace. You can have the best product in the world, but if people don’t know about it, it is useless.
Apart from actually launching the product, a PM should back up web sites or guides Of course you may not have put all those things online yourself.
2. Not investing in customer service

Even if you don’t work in a corporate role, it is still your responsibility to see that customers are satisfied with your product. You should be doing everything you can to ensure that people use your product and love it enough to talk about it.
This means that even before a customer complaint arises, you should be doing what you can to prevent issues from happening. For example, pay attention to how well your company responds to complaints when they occur.
If you notice that their response is slow or inadequate, maybe it's time to re-evaluate your position regarding customer support. People respond better to companies who seem like they care and want to help them, so making this an effort must happen within your organization.
3. Not educating customer

Education is one of the most critical functions of a product manager’s job, yet many product managers make it their last priority.
They spend time researching how to create best-selling products, instead of getting out there and educating people about what they do.
Education doesn’t happen overnight; it requires continuous effort to improve understanding.
The first step in fixing this mistake is for individual product managers to acknowledge that something needs to be done–and then work on doing it.
By working together, a team of product marketing, content creation, and training can help bridge the knowledge gap.
4. Not communicating well with key stakeholders

Communication is the most important thing for a PM. You must be able to communicate clearly and effectively with your teammates, whether they are people you know or members of another department.
Always err on the side of over communication.
Share roadmaps.
Very clearly say NO to feature requests but politely explain why there are other important things to do.
5. Not finding a champion from within

As a PM, you will have to work with marketing, sales, engineering, legal, accounting etc.
Promote your feature well within the company so that you have support from various departments. If you can't do so yourself, take the help of senior PMs or a mentor who can root for you.
6. Not giving feedback to Engineering leads

Your engineering leadership may not have bandwidth to focus on the product that you are building. You probably didn't get the best engineers for the product.
Provide feedback to engineers and engineering leads on a regular basis and raise the bar.
If you do not provide feedback, everyone will think that things are going well!
7. Not using prioritization framework
The biggest mistake that most product managers make is over-scoping.
Product managers should consider using a prioritization framework in prioritizing their tasks.
This will give the team more clarity in terms of the specific tasks they need to do.
It will also help with cutting down on scope creep and delays in the project timeline. A good framework is essential in getting things done on time and improving efficiency.
8. Not launching till the 100th feature works perfectly

We all know that perfection is the biggest enemy of progress.
It's OK to demo a slightly buggy product instead of no demo at all. Most learning happens when your customers use your product.
9. Not understand engineering culture

If you are working with well seasoned engineers or working on a product that was launched several years ago, chances are that the team is pretty comfortable with short user stories and not having finer details of acceptance criteria.
On the other hand if you are working on a complex product or with a new engineering team, chances are that you are defining the product culture and setting the bar for delivery standard. You (or product owner) may have to document minor details features, negative test cases, performance expectations etc.
10. Not sticking to short term priorities

Changing roadmap frequently does not inspire confidence.
You should have fair clarity on what is coming in the next 1-2 months. Changing priorities of features will also result in improper user stories documentation, bugs and eventually a bad software in the long run.
Bonus: Becoming a feature factory

Focus on the value delivered to customer. Become a value generation factory.
If you are given the choice between a larger number of features and fewer well-designed ones, choose the latter option.
Conclusion
Like any discipline, product management has its own challenges. The goal should be to get better every day. Here are some tips to get better.
Attend product management webinars. There are plenty of them happening every day and most are free.
Find mentors. Reach out to people who inspire you.
Give back to product management community. Join product management slack channels, discord etc and respond to questions.