About having to click on images to download them: it should automatically download pictures unless you don't have the sender in your contacts. Auto downloading on cellualr networks might be disabled by default though.
To say Signal is "unreliable" is bull shi*. It's a fantastic product and service that I would gladly pay for but am glad it's free. In the meantime I'll continue to donate as Signal has been very reliable in my years of use.
I have been using it for 3 years and struggle to recommend it to people because I constantly have reliability issues, including messages delayed for hours, bugs where contacts get in an unusable state and other little weird things.
Whatsapp doesn't have these issues, so even if it's due to not being online 100% of the time, Signal should deal with it.
Can you provide any issue you've submitted from years ago that hasn't been addressed? Please post it, I'd like to see.
Granted, a lot of these are probably outdated. However, given that there are literally >1000 issues closed by a bot, there must be some that are still valid but no one actually looked at it.