the key problem is that what they delivered is not needed by market.
I doubt that. Until now the blockchain's USP, as I wrote, wasn't delivered (not because it's a scam but because they clarified that at their roadmap, from the beginning). So currently the Ardor child-chains do not offer significant advantages to other "token" solutions.But once child chain pruning is delivered (testnet is planned still for late 2019 and mainnet for 2020), that would provide a crucial "maintainance cost" advantage to other blockchains, as initial blockchain download and full node RAM/disk space requirements would be much lower than for coins which do not offer that feature (the only exception is actually Cryptonite, an even much more smaller altcoin which has a similar system but without child chains).
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they need to accept advices from community to delivered a much suitable product.
Yep, that's just what I'm criticizing too: the decision-making is too centralized. They however accept some advices (a comment I made at Stackexchange probably inspired minimal-trust lightweight contracts, as they implemented a technique Lior had described in his answer) and perhaps even pull requests as they write on their Bitbucket repo.But generally speaking, I think the coin has not a problem related to missing features, but more of a communication problem. This thread, for example, is practically deserted, the Ardor forum has low activity, and there is confusion between the NXT and ARDOR brands (while Ardor isn't a particularly bad name, I would have preferred it to be called simply "NXT 2.0" as originally intended, but they cited intellectual property problems because of other NXT-named brands). And many ask themselves what the IGNIS token is meant for - the answer is actually that its utility depends also on the pruning feature as it would enable a lightweight payment sub-chain.
(or: Get airdropped high, sell low)
