It's Not Your Developer, It's You
The team at Sprintly, the makers of a productivity tool for development teams, have shared some interesting data on developer cycle time and it should calm your doubts about just how fast your developers are working.
Sprintly is used to track how long developers spend completing different types of tasks and the sizes of those tasks. Its recently published data reveals that, for the most part, developers are working at a pretty average pace (at least those using Sprintly).
Sprintly ticket data shows that across its user base, cycle times are very similar. 75 percent of all tickets in its system are started and completed in about 175 hours. Sprintly also found that most of the variability occurs before a ticket has been started - when stakeholders are the ones determining specifications and prioritizing work. There also seems to be a lag when transitioning from "done" to "tested and ready to be deployed.
That should put to rest at least some of your concerns that your development team is to blame for the slow pace of development. Sprintly's writeup on the issue delves into what's actually causing slow development, highlighting unclear and changing requirements as some common reasons.