I guess I'll be the one to disagree then, respectfully.
Weapon upgrades & customization should be earned by playtime, XP, or whatever. Leveling up is a core aspect of game design and has been since my days with the NES or D&D . And having to make compromises in how you build your character or kit is often a frustrating but necessary aspect of that.
For multiplayer games, it's especially important to provide incentives for players to work towards something that will ultimately reward them with a greater abilities and/or experience. Unlike single player or PvE games, BF6 can't buff opponent difficulty the more you play. The only thing they can do is to allow players to buff themselves through competition and play-based rewards. This has limits, of course, namely: (a) that progression should be reasonably obtained and not reserved solely for unemployed or incel gamers that have nothing better to do; (b) the rewards for such progression should be worthwhile but not unfairly advantageous to lesser experienced players; and (c) pay-to-win advantages are never acceptable.
So the only other option is give you everything outright. But things get boring AF real fast when that happens, not to mention being bad for business from an engagement standpoint. Moreover, game mechanics that require players to use tools they wouldn't otherwise use, or tools with certain limitations forced upon them, keep things interesting and prevent gameplay from becoming stale.
Everyone wants the Master Sword from the get go without realizing, or admitting, that it would just ruin the adventure. Similarly, every Helldiver (and I'm including myself) wants just one more strategem so as to address every scenario that may come there way upon landfall. But the latter game's developers tested that (including 5-man squads) and found that the current (frustrating at times) limitations and resulting compromises were what made the game fun. And crucial to team-based gameplay. 4-man squads with limited loadout options forces you to coordinate a squad-based loadout with each member choosing kits based on what their team is bringing and not bringing. You can't bring your super weapon and I can't bring that extra orbital nuke stratagem. We can't all be snipers and the team **bleep** well needs a medic, even if no one wants to play nurse today. So we coordinate, compromise and compliment one another. Games like these don't work when everyone can just pick their favorite Rambo meta without regard to the squad's needs.
My retort meandered a bit at the end, and I probably misinterpreted much of what you said, so I apologize if I did. However, your "everyone should have everything" argument just invoked some broader, related thoughts of mine on why constraints are necessary and beneficial in game design and creative arts, in general.
.02