The original version of BASIC was missing most of the features required for writing well-designed and maintainable programs of any size more than a few lines of code (basic data types like strings, data structures, functions with parameters, etc.)
Modern dialects of BASIC have many of these features but they are all different (there is an ANSI standard for BASIC but it has minimal coverage). Most BASIC dialects are still weakly typed which is a poor choice for large program development.
Yes, you can write large systems in BASIC but it's hard, they are less likely to be reliable, they are hard to maintain and they won't be very portable.
If you're writing small programs then BASIC is fine, especially if that is what you're familiar with. Beware though... small programs have a habit of growing
Cheers,
Rick.