Everything the show did well:
-Everyone in the hero side, from the rangers to the side characters are really likeable.
-One of the best team dynamics in the franchise, the show manages to make the most use of the team members being family members and stand out from the other 2 family Sentai shows.
-The rescue gimmick makes the monsters/cases of the week be constantly entertaining and heavily stand-out from other Sentai seasons. The show has enough budget to make proper use of this gimmick throughout the whole show for the most part.
-Really cool action from beginning to end, regardless if it's outside or inside the mechas.
-Better acting than usual Sentai shows make the emotional scenes in the show really hit.

Everything the show did bad:
-The show isn't the most unique due to following a lot of Sentai tropes and the villains while overall enjoyable not really stand out.
-The main antagonist is really generic and boring overall.
-Some elements of the plot points with team's mother feel contrived.

Reasons for the show's strengths:
Due to Japan enacting the Emergency Life-Saving Technician Law in 1991, the Great Hanshin earthquake in 1995 and the year this show was going to be airing, 1999, as 9 is pronounced the same as rescue, the core motif of this show being rescue was decided really early on and this show had more planning than usual. This allowed the show to have way more budget for its first 2 episodes and for them to try way more different approaches to action and setting throughout the show.
Main director Hajime Konaka wanted the team to show their face more often in order to make the rescue scenes more organic which is why the team has close up shot where you can see their faces through their helmets.
Main producer Jun Hikasa wanted the team to be family members taking inspiration from a show he previously worked on Yugen Jikko Sisters Shushutorian and another Toei produced show that was popular at the time Hitotsu Yane no Shita.

Reasons for the show's problems:
While main writer Junki Takegami is really great at character writing he tends to go pretty safe on the plot structure of his shows.

Overall:
While I feel that a lot of people would give this show an 8 due to not being that unique in its story department and being pretty safe overall. However the show's style, characters and dynamics are done so well and the rescue gimmick make the show stand out from other Sentai and easily makes it one of the best safe Sentai. Recommend this show to any Super Sentai fan or if you're into rescue/firefighting dramas or other rescue tokusatsu.