Entity for Capture Point:
/summon armor_stand ~ ~1 ~ {Tags:["neutral","point"],NoGravity:1b,Marker:1b,Invulnerable:1,Invisible:1}

ACTIVATE ONCE Commands:
/scoreboard objectives add capturePoint dummy
/scoreboard teams add Red
/scoreboard teams add Blue

Repeating Commands:
/execute at @a[team=Red] run tag @e[tag=neutral,distance=3,type=armor_stand,scores={capturePoint=0}] add redPoint
/execute at @a[team=Red] run scoreboard players add @e[tag=redPoint,distance=3,scores={capturePoint=0..99}] capturePoint 1
/execute at @a[team=Red] run scoreboard players remove @e[tag=bluePoint,distance=3,scores={capturePoint=1}] capturePoint 1

/execute at @a[team=Blue] run tag @e[tag=neutral,distance=3,type=armor_stand,scores={capturePoint=0}] add bluePoint
/execute at @a[team=Blue] run scoreboard players add @e[tag=bluePoint,distance=3,scores={capturePoint=0..99}] capturePoint 1
/execute at @a[team=Blue] run scoreboard players remove @e[tag=redPoint,distance=3,scores={capturePoint=1}] capturePoint 1

/tag @e[tag=point,scores={capturePoint=0}] remove redPoint
/tag @e[tag=point,scores={capturePoint=0}] remove bluePoint
/tag @e[tag=point,scores={capturePoint=0}] add neutral
/tag @e[tag=point,scores={capturePoint=1}] remove neutral
/tag @e[tag=redPoint] remove neutral
/tag @e[tag=bluePoint] remove neutral
/scoreboard players add @e[tag=point] capturePoint 0
/execute at @e[tag=bluePoint,scores={capturePoint=100}] run fill ~-3 ~-1 ~-3 ~3 ~-1 ~3 minecraft:blue_concrete
/execute at @e[tag=redPoint,scores={capturePoint=100}] run fill ~-3 ~-1 ~-3 ~3 ~-1 ~3 minecraft:red_concrete