Let face the UFP pratice terms did very little realitic plan for a Borg attack. UFP had every reason think Borg show soon. Borg alreadly destory outpost along netural Zone. Also add to it they alreadly know USS ENterpise D not armed well enough defend itself againist the Borgs. Found that matter even outpost along the Netural Zone not armed well enough defend themselves against the Borg.
My own thoeries why
While none explain it per a say
There limit what realistic could done came upgrade the USS Enterpise D or any other starship power and how big phaser bank put starship been Federation able to do one even entire fleet. Problem this one is does mean the UFP not try make powerful possible individual.
Possible reason first Section 31 get in way. Section 31 might plan Mars Defense Premotrs being what stop Borg. It is possible single one thing blow Borg Cube sky high stop tracks. Allow UFP fleet blow sky high might been part plan. All likehood even without Pircard help 40 starship destory. They might been even had plans us died Borg bodies for study real way defend against the Borg. Problems first Section 31 know Borg assimlate people unless TNG total not count Star Terk Enterpise this alternative timeline.
Federation still over convent saw Borg saw reason giving way life. Under this thoery even with the danger UFP still beleive no could harm them. They can take there time. While this thoery hit other end of the problems this thoery first if no other reason lead all other major power take action. For example Klingon Empire and Romulus Star Empire build up miltiery might one think this force the UFP do the same. With fact none major powers did that in Star Terk put this entire idea question. Like only UFP seen the Borg real threat getting readly even though slowly.
Those kind like two possible interest any other possible you guys come up with.