You can say "les moins riches", but as well, "les plus pauvres" is correct.
I see no problem in using "profite" instead of "exploite", however, there must be in the context an element which shows clearly that can be meant by "profiter de" but the synonymous sense of "exploiter"¹ (ref.).

¹_{Precision made salient by Gilles’SOnousesthostile’}

You may translate poorest communities with:

• communautés pauvres
• collectivités pauvres
• populations pauvres
• communautés démunies
• communautés défavorisées
• communautés dans le besoin

Please double check linguee to get some examples in different context.

Using directly Deepl:

Ce système créé par le gouvernement exploite les communautés les plus pauvres.

If you double click above pauvres you get several suggestions; among them are démunies and défavorisées.

If one do the sane for communautés he or she will get as alternatives to communautés the words collectivités et populations.

“Profite” is definitely wrong because it doesn’t have to be detrimental. There can be mutual profit, but exploitation is one-sided. There isn’t any significant difference between English and French here.

“System” should be “système”.

“Les moins riches” is not quite right: it encompasses more people than “poorest”. A straightforward translation “les plus pauvres” would be more accurate. However, the word pauvre is slightly pejorative (or maybe guilt-inducing) in late 20th/early 21st century French. Other adjectives such as démuni (which tends to apply to individual people) or défavorisé (which tends to apply to communities) are more common.

Ce système créé par le gouvernement exploite les communautés les plus défavorisées.