As a product manager, I am responsible for a part of a product in an organization. My team and I are always working on something critical with respect to the product. Part of the job is to keep the stakeholders informed. But an unspoken responsibility is also to showcase the work the team has done. It sometimes feels like tooting one's own horn, well it is, but it also serves other greater purposes.
Firstly, it is internal marketing, it helps the GTM(Sales, presales, customer success) teams know what is being shipped so that they inform their customers about this new feature or they can incorporate the feature in the product demo. Secondly, you are helping others in your team. Showcasing your team's work helps put your team in the leadership radar. It is not just for your sake, it is for the team's sake as well. If you showcase the team's work effectively, come next review cycle, it helps the powers-that-be to recall the person's team's work and help get a good review. Thirdly, it motivates the team. When you showcase the work, a team member might get a ping or at the water cooler, a colleague might come up to them and say 'hey, I saw the work you guys did, great job!'.
The trick to doing this without looking like a braggart is to pick the right moments, thank the people involved, talk about the value delivered with metrics if possible and the learning from the project. When it comes to right moments, end of quarter, end of 6 months into the year, thanksgiving or end of year are great calendar spots for this. Pick any or all of the moments above and write an internal blog. Be sure to thank the team members of your team and other teams that helped ship that feature. Mention learnings from shipping those features, there will always be learnings. Once you do all that, you realize that, honestly it is not selfish or boastful, you are doing a great service to your team mates, to your peers, to the stakeholders and to the whole company.