I am looking for the title of an old game

dungeon siege ?

............

Not much to go on - multiple CDs implies it was shortly before DVDs became standard.

Baldur's Gate came on 4 or 5 CDs, has a party which you recruit the members and played from an isometric viewpoint, but is not futuristic

Fallout Tactics maybe? You picked your squad before each mission, recruited people as you went on, it is kinda futuristic, albeit post apocalyptic and is isometric

Sounds very much like the original Syndicate games but I dont remember them being on a lot of discs but instead on 4 floppy discs if I remember right.