It is obvious that Defi can't go even further up than what it has done all because ETH gas fee is a lot. I for example had a token that I invested during presale and now I can't sell it because ETH is too crowded, it costs over 20-30 dollars just to get it out and I am not rich enough to invest 300-400+ dollars to make it worth while, which is why I am going to just keep it unfortunately, if one day eth fee finally goes down we could do a better.
Sure there are other chains but they are not used as much as ETH is used. Which means the moment you can swap without paying 40+ dollars, that would be a great period and defi will have a huge increase, think about swaping for under 1 dollars and paying 10 cents for eth transactions, if that ever happens (at this point I doubt it) that means we could do a lot better in the future and prices of defi will increase a lot.
I think there are two solutions to what you are talking about that will make defi once again bigger than regular centralized organizations.
One of them is to drop the price of ethereum costs, which will happen because miners are being a baby right now, they want their money and they want to make superb amount of profit from their gpu's without working, but that is not going to happen, the with EIP 1559 which they are complaining about, the extra fee will be cut, and it will be a lot better that way, we are going to see miners make less profit while transaction fee becoming lower and lower.
Secondly ETH will go towards proof of stake, which means you just need to arrange the blocks sizes and speed and so forth type of things and you will suddenly have a lot faster transactions without needing miners at all, it will be automatic. Lastly, all those other chains could get famous and bigger as well, that is another option, if ETH stays bad, other chains will get attention and get bigger.