Accessibility features are things that make it easier to play the game for those who are disabled or otherwise have access needs - These include things like subtitles for the deaf and hard of hearing, reticles in first-person games that don't involve aiming to help reduce simulation sickness, and icons on coloured blocks or cards that need to be distinguished for colour blind players. And, you'll probably have already noticed, some of these don't only help those they're intended for. Subtitles let those who have no hearing issues play a game while their partner or child is asleep in the next room, and icons can help people process the colour of the card that little bit faster. This is called the 'curb cut effect,' named after cutting away parts of curbs into ramps for wheelchair users, making towns and cities more accessible, also helped drivers be able to drive their vehicle into their driveways. An accessibility feature helped those who didn't need it for it's intended purpose.
Approachability features are things that make it easier to pick up and play a game, they include things like difficulty settings, helping those unfamiliar with a type of game ease themselves into it, strong tutorials that help teach the game's systems, making the spreadsheets in a management sim or JRPG look less like a spreadsheet and instead more inviting to use helps people not be overwhelmed by numbers. They help newer gamers and those not familiar with a genre get into a game.
Both of these are important, and while they do sometimes overlap, it does no-one any favours to conflate the two terms as we see happen time and time again.
As an example of how it's unhelpful to conflate the two - Nintendo is great at approachability. The Mario Sports titles are sports games that are easy to pick up and play, Mario Kart has various approachability features up to and including the stacking of item chances so you're more likely to get better weapons if you're further back in the pack, Smash Bros. is a fighting game where the controls are extremely easy to grok, with very few actions requiring more than a single direction on the analogue stick and a single button press. The success of the Wii was built on easy to understand motion controls for playing simulations of such things as bowling. The company tends to tune difficulty in single-player games on the easier side and often have methods of making their games easier still or skipping levels entirely - This is great for approachability.
What Nintendo is less good at, however, is accessibility. Motion controls are an accessibility nightmare since not all players can move their bodies in the same way. Even now that Nintendo has mostly moved on from games where motion control is the entirety of the experience, actions tied to 'waggle controls' - where motion controls are used where a button press would give the same game experience - such as Mario Odyssey's upwards cap throw and a lot of capture specific commands. Even something as basic as full button remapping is something rarely seen in Nintendo titles - Although console gaming has traditionally struggled to offer this in general, rather than just Nintendo.
But I sometimes see people surprised when it's pointed out that Nintendo is fairly bad at accessibility in general.
This just feels like an area where using terminology more accurately would help everyone.