Bringing a lot of weapons to the table can be a blessing and a curse. It can add immersion, diversity, and a lot of room for creativity, however it can also bog down performance, overwhelm, or just straight up be unfit for the title.
If you really want to immerse yourself in the world of a shooter, having access to a more personal arsenal tends to be really enjoyable. Whether it's a collection of weapons you might possess in the real and be comfortable with shooting, or just whatever weapons you've heard about and take interest in, having a wide selection can ensure your tastes are met equipment-wise, and you can always experiment with countless other options if you wish. In games that offer a shooting range or sandbox, having that wide variety directly at your fingertips is exhilarating. Being able to test all sorts of custom builds can help you build a style or refine a pre-existing one. In games that allow a wide selection of further attachments, it's really fun being able to spend hours custom-tuning a weapon to look exactly how you want it to. Really, it's a benefit to the player's imagination.
However adding a massive selection comes at the cost of increased performance requirements, which can be a problem for users with average or lesser machines. In more recent years, better tech has become more available and cheaper to the consumer, however even still not everyone has access or ability to get the high-end parts some highly diverse games require. Many weapons can also easily overwhelm most people. It can come as quite a shocker to users when they discover a massive list of possible loot, unsure as to what they're looking at or else just not wanting to go through so many things to find the right one for them. Additionally, some games are better off having a lower weapon count, like movement shooters and linear slayer-types.
However, as for myself, I really enjoy variety and diversity when it comes to most aspects of a game, like equipment and weapons for example. There is no clear "best," just situational opinions.