Love how people point out a couple situations where flash isn't mandatory, except even with those situations it is still a consideration.
To make it worse, can't unlock summoners until you hit a specific level, and yet they are so core to the current game that not having access to them is heavily punishing to low level summoners.
Summoner spells also restrict creative design of champs and items as they have to be balanced around summoners. I do think summoners should be removed as they are now. Making items to give similar effects might be an option, but as they are now they are not very interactive, not very fun and have little to no counter play. All of which are against Riot's design philosophies.
As a connected issue, Runes should also be removed for many of the same reasons. With the core of restricting champion and item design. They also create false choices for leveling summoners, but not having them can net upwards of 1500 g in stats lost. Also means summoners are spending IP on useless items in the long term when they could be unlocking more champions. At least runes need to rank up as the summoner levels so they only need to buy each rune once.
While the OP isn't the most eloquent in addressing the issues, the point is solid. Summoner spells are no longer good design and need to be removed at least until they can be better designed, if not permanently.