Submission Limit. If you are only trying to add a few pages at a time, GSC is effective. But if you need to index more than 10-15 pages per day, Google will block your access. This can be especially problematic if your pages are suddenly deindexed and you are looking for a rapid solution.
Limited Use. If you do not have Google Search Console access for a URL, you cannot use their tool to index content. For example if you are trying to make sure a social media post is indexed or if you are trying to index a third party blogging platform (i.e. Medium).
Indexing is Not Guaranteed. Although submitting an article to GSC is typically effective, Google does not guarantee that it will index any specific page.