I don't think this is related to SQL Server 2025, but rather it is a limitation in SSMS 21, see https://techcommunity.microsoft.com/blog/sqlserver/sql-server-management-studio-ssms-21-is-now-generally-available-ga/4415230, and particularly the section SSIS and Maintenance Plans:
We made the difficult decision to hold back SQL Server Integration Services (SSIS) support for this release. This includes the import/export functionality and Maintenance Plans. In the spirit of full transparency, during the final weeks of testing, we recognized that SSIS needed additional time to ensure the quality and stability our users expect, so we made the decision to temporarily hold it back while we continue to enhance the experience. Our primary focus for SSMS 21 was to move to Visual Studio 2022, provide initial support for SQL Server 2025 Preview, and support the Copilot in SSMS Preview. Our team is actively working to bring these features back in an upcoming release. For now, if you rely on SSIS we recommend using SSMS 20, which you can install side-by-side with SSMS 21 GA.