I take it you are not liking the latest version of Excel for Mac very much.
If you haven't updated lately, then do so. The current update 15.26 is 64-bit and runs noticeably faster than the 32-bit version. It's no speed champion, but it is a definite improvement. My recommendation for using Excel on a Mac is to have a minimum of
16 Gig of actual RAM (double that if you are using Parallels or if your workbooks are large and/or laden with objects). Macs that don't have video cards and rely on INTEL graphics rendering use the CPU to manage the screen and screen RAM. This is hopelessly
slow. A mac with a fast video card with dedicated video RAM will work much better.
Microsoft has a free version of Microsoft Excel to compete with Numbers, LibreOffice, and other free products. It's a stripped down version on line at docs.com and onedrive.com. It's sharing component is very good. I like the survey feature. But it's targeted
toward the same markets as the other free apps - light duty users such as housespouses, students and teachers. Like the other free spreadsheets the free version is feature sparse.
For my own purposes, Excel for Mac has about 1/3 of the features of Office for Windows. When the VB Editor finally comes around I'll boost that up to about 1/2. Where the 2016 Mac version really falls down is data analysis. It lacks all of the power tools
and has no SQL editor except for a text editor that replaced Microsoft Query. Very sad, indeed.
With regard to extensibility - none of the free alternatives offer much in the way of extensibility. You get completely broken VBA in LibreOffice and no security at all for VB code. Mac Excel supports VBA, AppleScript and Javascript. Windows Excel supports
VBA and Javascript but not AppleScript. Microsoft has promised to restore the 2011 VB Editor to Excel 2016 some day - a day which has not been specified. There are more bugs in VBA on the Mac than in Windows, but the actual number of crashes and bugs does
not seem to be terribly large is my conclusion based on the relatively few problem reports I've seen here in the forums. If you're getting a crash from VBA code, then I suggest posting a question that addresses your crash - include code snippets and steps
to reproduce. Always be sure you're including the version and build number in your questions, as Microsoft is actively fixing VBA bugs and each update comes with its own unique set of bugs.
As for Excel 2016 for Windows, I think it rocks. It's fast. It has a whole lot of features missing from any other spreadsheet product. I agree with your assessment about chart formatting in Excel for Windows. I often make charts in Windows Excel, format
the charts in Mac Excel, and then return to Windows Excel for most everything else. You can format just about every aspect of a chart, so if you have an ugly chart, I point my finger at you, not Excel.