The biggest red flag about what you're saying is that it implies work done by the team (junior or not) isn't tied to specific goals our outcomes for the organization.
Having work sit in branches un-merged for an indeterminate amount of time is terrible management and a terrible work culture. Your org sounds rudderless.
I'd suggest revisiting your roadmap and sanity checking with your stake holders that the work devs are doing is actually meaningful, and regularly calibrating amongst yourselves with agile ceremonies such as backlog grooming, sprint planning, daily checkins, retrospectives and internal demos/UAT.
Even if you don't follow an agile process, regular (ego free) retrospectives with your team mates is the most beneficial of all ceremonies.
I'm not calling out junior devs here on purpose, it seems like an organizational culture problem tbh, and your senior devs are not acting very senior by failing to mentor and assist younger team members ;)
