Hi there thanks for posting in Community. Unfortunately this is expected behaviour when resizing the standard Lucidchart cylinder shapes and there is currently no way to change this behaviour (aside from creating a similar custom shape as you already mentioned.) I apologize for the roadblock and the poor experience here. 

Would you mind submitting this feedback to our feature request form? This feedback goes directly to our Product team so this is the best way to directly submit a change or improvement you would like to see. 

Has this been implemented?

Hi Yoav

Thanks for your question!

To resize a shape you can select it and drag one of the blue squares along its border. Hold down "shift" to maintain the shape's dimensions/ratio while resizing.

Scaling a shape as described by cheng.ngai above is not currently supported. Please make your voice heard and fill in our feature request form if you'd also like this feature to be implemented! The more users request a feature the more likely it is to be made a priority by our Product development Team!