Super computers are a reality already Quantum computers on the other hand break a lot more things but that’s a separate topic of discussion. Note that it’s not that quantum computers are more powerful but it’s more like they do certain tasks better than classic computers.
However the weakness of Monero is not the encryption which is based on generally solid cryptography but on its design in using ‘decoys’.
Monero has been transparent on its weaknesses and an excellent resource is Breaking Monero and of course are constantly improving.
That said they do have a lot of things going for them such as mandatory privacy, high transaction volume and enforced stealth addresses that make them practically very private today despite the limitations of the tech.
And you’re right, Monero’s first few years were completely deanonymized due to their use of 0-mixins and also until RingCT was fully implemented, still had a bunch of ways to reduce anonymity.
Lelantus is the other way around. The tech is pretty private but it’s still growing up. The first version of Lelantus v1 which we have deployed while the official wallets prompt for ‘on-default’ privacy, it isn’t mandatory. The output amounts are not hidden yet although the change amounts are. Full hidden output amounts is coming this year in Lelantus v2. The anonymity sets that we use are probably big enough to prevent the decoy issue. Moving to mandatory privacy is also the aim but will require time as we need to figure out how to do interop/masternodes.
That combined with Dandelion++ (today) and future mixnet integrations I think it would provide pretty high levels of privacy.