you are 100 percent right. Yacht electronics manufacturers today expect to sell you a new set of instruments every five years. Not only do they want to sell you a single instrument that has failed they want to sell you a complete new set of instruments. That is why they keep changing the look of their product.

The day Raymarine separated from Raytheon they would not service anything labeled Raytheon even though they were making the very same products.

Their primary customer is the weekend sailor and they expect them to call their local dealer to get a problem fixed. They are almost completely unresponsive to the needs of cruisers away from their dealer support. The stuff is made as cheaply as possible and when it breaks they either tell you to buy a new one or completely replace the circuit board for a very high price. Mil Spec it isn't, marine environment protected it isn't. A ten cent resistor failure drives a $200 board replacement even if they can see the burned component. These days even the dealers have no schematics - they are expected to send the units to the manufacturers service office for board replacement.

I have a lot of electronics and do not tie anything together unless it is necessary. Other than the GPS feeding the computer, VHF, Radar, etc. and that is all standard NMEA0183 so I can easily swap a different GPS if I need to.

When it comes to keeping the older stuff alive used sailing equipment stores and Ebay are your friend.