In my opinion, it would be better without the signature campaigns, for sure it would be a normal forum without any money involved so most of the users would just post for knowledge, experience, questions, tips, etc.
I beg to differ, i don't think the forum would be better without signature campaigns, let us be honest, the forum activity is going to drop quite significantly if that happens, thus who is going to share knowledge on the forum or answer important questions of newbies about Bitcoin. Signature campaigns and the merit system are two things that have helped this forum greatly to maintain its high standards, to join signature campaigns you must earn merits, and to earn merits you must make HQ posts. Mind you that there are spammers on every platform, and even if there's no signature campaigns here there'd still be spammers, thus if you think spam posts are a problem in the forum, use the "report to moderator" button more frequently.
I've mentioned most of what you said, It will surely drop down the forum activity as well as users but it's better to have a low organic discussion than having a lot of discussion that is just some nonsense discussions. I mean you know what I mean most of the discussions on the thread don't make sense, repetition, or just sht posting.
Merits somehow work on making some high-quality posts on the forum since most of the users are spamming to make a lot of posts because back then you just need a certain amount of posts to rank up. At some point signature campaign actually is a great motivation because it can be a part-time job, but still has bad effects at the same time.