Some people aren't quitters. They don't just quit whenever something stops going their way, they try to change it, try to improve it, try to make it better, even if the only way they have to do that is express why its not best.
Be more like them.
We do try to improve products we use but in this story unfortunately you don't have a voice because if you're not an advertiser. Think about how much ads you need to sell to earn 1B back at least and sustain operating expenses especially when you're not trying to be lean with your resources.
As IG user you have only one right, to say "yes" to any changes they want and to obey to the algorithm of banning and censoring. You don't have any right if you can't enforce it. They can ban end censor your opinion and can enforce this right, you can't do anything about it. You are the product they're selling after all and they care about you in terms of as much revenue you can generate on this particular platform (macro picture of user retention).
Can't get why some users don't like the change. You're free to decide should you use a product or not. To put it from other perspective, you choose to become a product for instagram to sell or not. If you don't have an account, it's hard to earn more from your time spent in the app. Billions doesn't ROI themselves.
Old web is still there, forums/personal websites isn't banned. You still can do things the old decentralised way probably to a greater extent because internet is even bigger now.