Exploring apps can be challenging.
We'll need to work out why the spiders are not exploring the relevant sites effectively, and its best to focus on one site at a time as the reasons may well be different on different sites.
So pick the site you most care about and focus on that (or pick a random one if you dont have a preferance;).
Some initial questions:
* Does the site use authentication?
* Do the 2 spiders find similar pages?
* Can you tell if its a modern web app?
* If you launch the ajax spider using a non headless browser can you see which links it is failing to follow?
As for alternatives, proxying regression tests through ZAP is always a good option, if you have any. You can do that before running the spiders to seed them more effectively.
You can also import APIs is you have a definition for them in OpenAPI/Swagger, SOAP or GraphQL...
Cheers,
Simon