It seems you are talking about the Inscription trend on the Bitcoin blockchain. They have caused network congestion and pushed transaction fees to very high levels, even $20 per transaction. However, we are seeing the rise of Layer-2 solutions on Bitcoin such as Stacks, Liquid, RootStock, SatoshiVM..., this will be a new home for Inscription and the Bitcoin network will be peaceful for basic purposes.
The fees have actually reached almost double the amount you mention, but it should be taken into account that the fee depends not only on the current state of the mempool, but also on how many inputs/outputs you have in your transaction. This means that transactions can be quite expensive for some if they have a lot of so-called
"dust transactions" and for those who don't know that in some wallets there is an option called
"coin control" with which we can very precisely spend exactly what we want and thus avoid a large transaction price.
As fees decrease, users will benefit from sending BTC to the address specified by MixTum. I even hope that MixTum can lower the minimum cost in the future, 0.0007 BTC can be reduced to 0.0005 BTC 
Look, it can always be too expensive for the one who sends it, but we have to take into account that the mixer has to somehow make money for all the costs it has, as well as for some kind of profit, which is why such a service exists.
What I can say is that if MixTum does well, I assume that it will provide even better conditions for users in the future.