1. You're not being as effective a leader for your team while your attention is on your own individual contributor-level work, and
2. Your people aren't getting the learning experience of tackling the difficult jobs themselves, which means that the same thing is probably going to happen again the next time this kind of difficult blocker turns up.
In essence, you're getting a better result in the short term at the expense of better results in the long term.
And don't get me wrong -- sometimes that's the right choice!
I feel like one of the marks of a really strong working manager is the ability to recognise whether a situation is so critical to the company's survival that they (the manager) needs to handle it personally as a matter of simple survival, or whether they can get away with delegating it to team members who perhaps won't do as good or as quick a job as the manager themselves could, but who will learn and grow and improve as a result of being given the challenging task plus mentoring and feedback.
Most of the time, the most important, impactful thing a leader can do is to deepen their bench; increasing the skill of your team pays dividends for decades, even long after you've been further promoted or left the company.