Project 677: Lada/Amur(export) class submarine

Is it possible to praise the work on one design without trashing the work of others, pretty please?

Well lets be honest... a lot of the trashing of AIPs comes after certain members claimed an SSK is not a modern SSK unless it is fitted with a working AIP.

The best AIPs operational anywhere are nuclear propelled subs, but they are also rather expensive and not every country can afford to operate them let alone develop and produce them.

Introduction of AIP was an huge technological and operative step forward for the times it was developed and put in service.
Obviously, different solution were tried, some worked excellently, some were in time abandoned.

To be fair most HATO AIP subs will be ambush and terrorism subs so having two or three days every two weeks when they are not much use is not really a huge problem for them, but for a Russian sub that is patrolling local waters a 4-6 hour gap while running diesel engines and charging the batteries is an acceptable price to pay because obviously they wont be on their own and they wont all charge their batteries at the same time.

Looking to the future they are talking about sea bed based recharging stations for SSKs and also drone subs, which means all the space AIP systems take up could be replaced with more new battery types... when attached to the charger and charging batteries they can clean the onboard air supplies and have everything running in passive mode listening for threats and targets while remaining stationary and charging the batteries.

Or they could simply develop a tiny SSN whose purpose is to operate in each of the four main fleet that is a mobile battery charger that can rendezvous with SSKs and various drone types underwater to charge them without needing to surface at all. The connection could just be to transfer power or it could include the ability to transfer people and material so you could forward deploy SSKs somewhere and these SSNs could operate as sub tenders to support their operations.

decided not to pursue such way anymore?

Too dangerous and not as good as nuclear powered subs which are rather faster and with much better endurance at the cost of being more expensive.

Well, that means that such a thing have certainly a sense FOR THEM, for other countries situation could be different and continuing following such a way could EQUALLY have a lot of sense FOR THEM:

European countries seem to not like nuclear power, and AIPs might suit them better, but that is in no way to say an SSK is useless without AIP, which is what many advocates of AIPs suggest when whining that the Russians don't have any operational at the moment.

Sorry, in what part of my post you have seen the world "success" referred to Quebec class?

That is the problem for the Soviets/Russians, something the Swedish might consider successful just might be a total failure for Russia, but then the Russians will spend on defence when they think they need to... now Sweden is part of HATO it is going to realise defence has nothing to do with defence or capability and is more about buying good will from the countries you trade with in the West. Buying French subs will get you in good with France and buying subs from the UK and US will get you in good with them, but the budget will be enormous...

The sonar systems and other sensors and weapons are similar to the stuff they put on their SSNs so an order of performance above what SSKs normally get.

It should be a very good sub... but then Improved Kilo class subs are still good enough for many missions anyway.