AE creating 500+ groups when creating shape from vector layer

There are limitations you must be aware of if you want to convert a vector layer to a shape layer. Here they are:

1. Simple stroked paths will successfully be converted to paths with a stroke that matches the stroke width and fill color in Illustrator.
2. Paths that have any kind of simple brush applied will be converted to a closed path that outlines the shape the simple brush makes on the canvas. The center path will be lost.
3. Any Art Brush in illustrator that creates multiple shapes will be converted to multiple closed paths in Illustrator. If the brush creates hundreds of shapes, you will end up with hundreds of paths, each in its own group.
4. Any Gradients created in Illustrator for a fill or a stroke will be converted to a solid 50% gray fill. Gradients are not supported in any way. You will have to replace them manually.
5. Unless you are using shape layer animators or animating the actual vector path, or extruding the layer, there is no advantage to converting a vector path to a shape layer.

The workaround is to create a copy of the path you want to reveal on a separate layer, remove the brush, make sure that there is nothing but a simple path filled with a solid color on that layer, Name the layer Track Matte, then Import the AI file as a composition retaining layer size, open the composition, convert only the Track Matte layer to a Shape layer, then make sure that the Track Matte path's stroke is wide enough to cover the entire path, apply trim paths, and set up the matte to reveal the brush stroked layer.

There is another workaround if you absolutely need to convert complex AI paths to editable shape layers in AE. The workflow is a little odd, and I recommend that you create a copy of the AI file that only contains the layer that you want to convert to a vector path. In the situation you are describing, you would duplicate the AI file, remove all layers but the one you need to convert to a shape layer, and then save the file appending the file name to something like MyFile-xd.ai.

Now Open Adobe XD and make sure that After Effects is open. Start a new XD document that is the same size as your comp. Go to File/Import and select your MyFile-xd.ai and let it open in XD. Now select the part of the file you want to add to After Effects and select File/Export/After Effects.

A new AE comp will be created inside After Effects that contains all of the elements you selected in XD as Shape layers. All Strokes, Brushes, gradients, and other elements will be there. You can then copy and paste the layers into the Main comp or just nest the comp created by XD and do the shape layer animating there. 

There is no need to save the XD document. The only purpose of the workflow is to create an AE comp with all AI layers converted accurately to shape layers. Be careful with the complexity of your file. You could end up with thousands of layers. 

Yeah, agree with the pixel smithy. Without seeing your artwork nobody can advise on how to best proceeed and chances are that you are going about this the wrong way, anyway. Unless your clip is several minutes long nobody would even see those 500 or more shapes being drawn on. Human perception just doesn't work this way. In turn that means that there's a good chance you won't even have to convert considerable chunks of the artwork and instead can reveal them using conventional methods such as track mattes, simple linear and radial wipes, mask animations, the Stroke/ Write-on effects and so on. Basicalyl everything that a "logo reveal"/ "swirls drawing on" tutorial from 15 years ago would have used. Those techniques are still valid and it seems people all too easily fall into the trap of prematurely converting their AI files just because they can these days... Anyway, show us your graphics, the AI layers palette and all that and we can tell you more.

Mylenium

What you are encountering is simply the way converting to an AE shape layer is handled. 

The basic issue is the there is no equivalent in AE to Illustrator tools like brushes.

A single shape on your imported layer would be converted into a single shape by the AE converter, but the more objects you have on the illustrator layer, the more groups you get when you convert them. Basically, the more compex the illustrator file the more groups your will get after the conversion.

So if you have an AI layer composed of 5 simple shapes, you get 5 groups when converted. In this case a group could be a single object or multiple ones.

Now think of Illustrator artwork like brushes, patterns, etc. While in illustrator they are treated as one object, when converted into an AE shape each individual path (that made up your brush stroke for example)  is a separate object, and you get lots of groups from that. 

So the only way to limit the number of groups you end up with after the conversion if to limit the number of individual paths on the layer you plan to convert. Depending on the graphics yo might be able to use Illustrator tools likepathfinder to combine shapes together.

Depending on the AI graphic it may be possible to simplefy it, but without seeing the graphic no one could give you specific advice. 

There might also be a way to animate what you want in AE without converting it into a shape layer. Again it depends on the content of the graphic and the animation you want to make.