Yeah that's kinda the point of the bomb game mode, you have to protect it and you're given barricades and all sorts of tools to set up with. The trick as the attackers is to be coordinated in your breaches into the defended area so you're not picked off one by one and to cause confusion and misdirection where possible.
There's so many different tools available across all the characters, if you're just going in blind with guns then you'll die to a good defence, you need to do stuff like set breach charges on one side of the room and then run around to another breach point and then set off the breach charge to distract people and make them think you're breaching from one side, then bash in the door and hit them from behind. Scaring and confusing the campers is super easy with greandes, you can even wheel in little remote controlled drones to survey the area (after the initial setup stage), throw in smoke, or stun grenades.
There's a lot of nuance to the game when you start to realise the complexities of it, for example most people carry breach charges but the defenders can erect shielded walls which stop those charges from blowing holes in the wall, but then one of the attacker special classes has a thermite charge which can burn through that wall, it has a burn time of 3-5 seconds which alerts them you're coming and a great tool for misdirection since it gives them time to focus on it while you rapel in through windows behind them.
Coordinated beaches with shields is good, the shield doesn't carry breach charges I don't think, so if you work together with someone with them, they can breach for you, the sheild goes through first and soaks up all their fire, and then immediately behind the shield you want another 1-2 people run in behind his cover with assault weapons
You need to play a few games and get some renown (you can get some from just watching the tutorials) and unlock some of the characters to use in multiplayer, it's the characters special abilities that make the game really.
Having said all that, the actual beta looks like a total mess right now, a 4 day beta isn't long enough to learn anything significant, lots of people didn't receive their activation key even being guaranteed one via pre order, so it looks like this might become a hot mess pretty fast if they don't do some damage control.