Would matrix support in BASIC have reduced VisiCalc's popularity?

I don't think it would have, with the caveat that I'm only familiar with the BASICs of the 80s and 90s (my first language was QBASIC and I also learned Visual Basic 6); I wasn't around in the 70s and I know little about the BASICs of that era.

I think a major part of the appeal of VisiCalc was introducing the now-familiar spreadsheet UI to people. Yes, anything I could do in a spreadsheet I could also do with a general-purpose programming language, including BASIC. In fact, from time to time I use Python instead of Excel. However, spreadsheets are more accessible for non-programmers, and even for programmers there are many cases where the UI/UX of a spreadsheet is more convenient, just like how there are some tasks where I prefer LaTeX over Microsoft Word, and other tasks where the reverse is true.

There’s a fun product management story that I forget where I read about how Microsoft discovered that most people who used excel weren’t using it for calculations. They used it to make lists (well, tables).

It’s the visual grid that people find useful, at least as much as the quantitative tools.