In order for this to gain traction and meet the requirements of the Ideas boards, we need a bit more information about your Idea. What specific functionality is missing for you?
The main functionality that is missing is having the attribute table format for Shape Files stay the same when uploaded to ArcGIS Online as well as when downloaded from ArcGIS Online.
Right now there are things that prevent it from being that smooth like for example layers created in ArcGIS Online having a way longer character limit for field names. On ArcGIS Pro with shapefiles the character limit for field names is only 7. This means that when a layer is downloaded to ArcGIS Pro it will automatically have its field names truncated. One of the many issues created by this is that if you want to download a layer created in ArcGIS Online and edit it to be updated on ArcGIS Online, it will also truncate the field names on ArcGIS Online.
I have also run into a few other examples like the data types list being different when creating field on both, the number format settings being mostly absent, ect.
The biggest issue to me is the attribute table names as that has caused me tons of headaches in the past and if these differences are intentional, neither piece of software really tells you about them so they are a surprise when you run into them.
That's unfortunately a limitation of using shapefiles. Their fieldnames are limited to 10 characters and they don't get the fancier new field types. As a format, they're 30+ years old. (They also are limited to 2GB of data.)
The feature services share largely the same limitations as feature classes that live in a geodatabase (@esri please give us a vocabulary word for geodatabase feature classes-- I'm partial to "GDBFC"), as far as I know. A feature class that lives in a geodatabase can be 1TB in size, have field names of up to 64 characters, and gets the new field types.
Shapefiles are great, and there's a reason that they're still in use today. However, they're really limited in what they do. In my experience, the best use of them nowadays is sharing data by zipping and emailing them. That being said, mobile geodatabases (or geopackages, for the non-Esri flavor) have all the advantages of file geodatabases, and are just one file, so they're even better for sharing data, since the field names don't get truncated (like what's happening to you). The only real disadvantages in a mobile geodatabase are that 1) the geometry doesn't get compressed, so they get big quickly and 2) I don't think there's raster support.
All that aside, this could be solved by just tweaking your workflow to make whatever you're doing in AGOL match the limitations of a shapefile. If it can't have fieldnames longer than 10 characters, don't make your copy in AGOL have field names with more than 10 characters. Ditto for field types.
One thing to note that the documentation doesn't make clear: A shapefile is a container with 1 feature class in it. Because it only contains one, we often call the feature class a shapefile, and call feature classes that live in geodatabases "feature classes". Both are feature classes, and the limitations on them are a result of the container they live in.
@AlfredBaldenweck gave quite a complete answer to the question here.
Shapefiles are a legacy format. The field name length limit is a limitation of the format and not a limitation of the attribute table. Similarly, newer feature like the new field types available in ArcGIS Pro 3.x are not supported. As @AlfredBaldenweck mentioned, geodatabase feature classes share most of the limitations of feature services, with some caveats depending on the workspace type.
Enhancing shapefiles to support the new field types and longer field name lengths in not on the development roadmap.
The limitations of shapefiles can be found in the documentation linked below.
