Hello, can you provide some details about this? What errors are you getting? What actions are slow? Does this happen all the time or just sometimes? When did you first notice this issue?
No, this was announced in February and ample time was given for all users to migrate their processes to the new tools: Removal of legacy developer tools
You're running into limitations using the Developer Tools as a workflow tool to extract large amounts of data, but the tools intended use case is a quick way to testing basic API functions before consuming them in your own applications. Your browser can't handle syntax highlighting excessively large payloads (i.e. larger than a human can functionally read), which is what's causing it to hang. CX as Code or using the API/SDKs in a custom script or application are good approaches for handling/exporting large amounts of data.
If you really are just trying out the APIs, set your page size to 10 or so to limit the results to an amount of data you'll be able to read and your browser will be able to render.
That said, you're definitely not the only person attempting to use the tool in this way and we do have an item on the backlog to disable syntax highlighting for large payloads.