I've been playing sonic 4 recently, and it shows up all the same problems. It's so focused on matching the 2d platformers it even replicates some of the most frustrating elements of them.
Having said that, Sonic 4 episode 1 made me feel like they were overdoing the 'we can do HD graphics now element, isn't that great!?' - even though everything is hyperdetailed, it doesn't look that good, and I felt it lost the charm of the originals...
(Episode 2 is better because it's 3d background elements seem to be actual 3d background elements, and not clunky pre-rendered sprites)
Especially still prominent is quirky jumping over bottomless pits... Get it even slightly wrong, and you fall to your death.
Only the jumping mechanics sometimes don't want to cooperate.
Or, some platforms in at least 1 level have dubious hitboxes, and enemies standing on them in a weird way that you need to use the lock-on ability that Sonic 4 has to get by...
Only... The lock-on ability in some cases can be really flaky in itself. So... If you fail to land on the part of the platform you can stand on (it looks bigger than it is), you die. If you hit the enemy without being in a spin attack. You die. (impossible to recover the hit even with rings, because you fall).
If you try to use the lock-on, unless you are exactly perfect with it in a way you usually don't have to be, you hit the enemy, lose your rings, and fall off the edge.
And you need to do it about 10 times in a row, with the same level of weird, unreliable lock-on for each jump...
Yeah, sonic has a tendency to have a few dubious sections like that no matter what game you're talking about...
But... Then I dug out the genesis collection on steam, and played the first sonic...
And boy, was I ever wrong. The 'charm' of those graphics turned out to be a lot less charming than I remembered... Super Mario World looks considerably better these days than Sonic does...
It's not so much the lack of resolution, but the really obviously limited colour palette that, while being used with considerable care, still show through their limitations...
Also, lack of the spin dash... Which is an addition from Sonic 2... And boy is it ever clear why they added it. Sonic 1 can get absurdly frustrating in places because the inertia mechanics mean you can get stuck if you don't have the space to take a run-up at something.
From sonic 2 onwards, the spin-dash can get you out of these situations, but in sonic 1 you're just forced to figure out a way around it if you get stuck like that...
Still, the level designs of those old sonic games were quite impressive.
One thing you learn with experience though? Sonic isn't about speed. OK, yes, it has sections of crazy level design which exist solely to show off with that speed, but the reality is, the game punishes you for speed, especially in later levels.
Sudden drops that you don't have the reaction time to avoid.
Spikes at the end of a long run that if you take the section leading up to it at speed you'll run straight into...
In fact, sonic, as a game repeatedly tries to lure you into going fast only to punish you for having fallen for it.
Sonic is weird like that...
It uses it's speed as a weapon, something which looks impressive, only to lure you into using it when doing so will only cause you harm...
Or... At times, punishing you for not managing your momentum in general, even if it is a section where it demands top speed, you have to get it just right...
Keeping in control while living with the constant temptation to go completely out of control. That's sonic...