The imagery on ESRI products is extremely poor at least in comparison with google imagery. See the screenshots below:
Is there better imagery available that could be accessed within ESRI products, especially web; and if not, is one able to utilise their own separately purchased imagery in web products for example experience builder?
There are many sources of imagery as web services.
For example in Australia, Queensland, the Department of Resources publish a time-series image service that you can use in Pro. Other states and jurisdictions have the same.
These could be in image services, map services, or non-Esri WMS or tile services.
Ask your local council, county, state or federal government agency if they have image services published. It will usually fall under the mining/resources or Environmental themes.
These will likely be the most up to date and can be very high resolution and used in web app products.
I have not found many set up to use as offline basemaps for Field Maps - Ymmv.
Look into services such as Arlula that will help you buy satellite imagery from archive or new tasks for small areas.
To use your own imagery you have to create a tile package and upload/publish to AGOL.
Let us know if you are familiar with that process or not. There are catches with regards to best use of credits in AGOL when publishing image services.
The ArcGIS Living Atlas of the World has high spatial resolution in various formats you can access here - ArcGIS Living Atlas of the World
For example, the World Imagery layer:
The map is currently comprised of the following sources: